Band 114, Heft 1

The widespread presence of sodium in the earth’s crust, the significant stability of its compounds and its great ecological recycling possibilities are all factors that lead researchers to new structures exhibiting ion migration of sodium and high electrochemical potential. The present research shows a new way for Na 3 Fe 2 (PO 4 ) 3 synthesis with Na S uper I on Con ductor structure. The use of ferrous oxalate precursor Na 3 Fe(C 2 O 4 ) 3 changes the reaction pathway of the iron-phosphate system synthesis and leads to the formation of a structure that allows ion migration that enhances electrochemical charge storage properties. At best the measured capacity was 85 mAh g −1 over a voltage range of 4.2 V–1.5 V versus Na/Na + . It is shown that the presence of colloidal silicon dioxide helps the main phase crystallization, without entering its structure.

LiMn 2 O 4 has the advantages of low cost and no pollution, and is widely regarded as a large-scale lithium battery cathode material. However, the capacity decays rapidly, which seriously affects the application of LiMn 2 O 4 cathode materials. Therefore, improving the cycling performance of LiMn 2 O 4 is the focus of current research. LiMn 2 O 4 precursors were prepared by chemical precipitation and the precursors were coated to prepare LiMn 2 O 4 /TiO 2 composites. X-ray diffraction and scanning electron microscopy showed that LiMn 2 O 4 had been successfully combined with TiO 2 . Electrode charge–discharge and electrochemical impedance tests showed that LiMn 2 O 4 /TiO 2 had the best cycle performance at high rates. The initial discharge capacities of LiMn 2 O 4 /TiO 2 reached 106.4 mAh·g −1 at 0.2 C. After 100 cycles, the 2 C capacity retention rates was 76.3 %, compared to only 66.5 % for pristine LiMn 2 O 4 . The improved electrochemical performance was attributed to the nanoscale oxides hindering the reaction between the electrolyte and the electrode, which effectively improved the stability of the material during high current charge and discharge.

Ternary conductive ceramic Cr 2 AlB 2 phase has been widely studied because of its unique physical and chemical properties. However, the preparation of conventional synthetic Cr 2 AlB 2 requires expensive raw materials or higher equipment cost, which is not conducive to its synthesis and promotion. Hence, we synthesized high-content Cr 2 AlB 2 by thermal explosion reaction, a technology with low-energy consumption. Cr 2 AlB 2 was synthesized by thermal explosion reaction from Cr/Al/B mixed powders. The effects of different ignition materials and diamond additive on Cr 2 AlB 2 synthesis were studied systematically. Results showed that the Cr/Al/B system did not undergo a thermal explosion reaction. An aluminothermic reaction between Al and Cr 2 O 3 occurred by introducing a small amount of Cr 2 O 3 . The main phase of the thermal explosion products of the Cr/Al/B/Cr 2 O 3 green body was CrB. The addition of an appropriate amount (7.5 % and 10 %) of diamond in the raw material can obviously promote Cr 2 AlB 2 synthesis. The main phases of the product were Cr 2 AlB 2 and CrB. The samples were composed of a large number of fine Cr 2 AlB 2 lath grains. Finally, the mechanism of Cr 2 AlB 2 formation by thermal explosion reaction was proposed.

This study presents a facile method for preparing low-temperature gas sensors based on nanostructured Ag-doped and In-doped vanadium pentoxide (V 2 O 5 ). Pure, In-doped, and Ag-doped V 2 O 5 samples were synthesized using the thermal decomposition method, and thermogravimetric analysis was used to determine the optimal calcination temperature. All the samples were characterized and analyzed using field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Both Ag- and In-doped V 2 O 5 exhibited higher sensitivity toward ethanol compared to pure V 2 O 5 . Hence, incorporating metal ions into semiconducting metal oxides holds the potential to enhance the sensitivity of gas sensors.

Erbium-doped zinc oxide (Er-doped ZnO) as a visible-light-driven photocatalyst was prepared by combustion method and followed by calcination at 600 °C for 2 h. The samples were characterized by means of X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. X-ray diffraction patterns of ZnO samples with and without Er dopant confirm the formation of pure hexagonal wurtzite ZnO phase. The X-ray diffraction peaks of ZnO were shifted to the lower 2 θ angle when Er was doped to ZnO matrix. Their transmission electron microscopy images show that the addition of Er can play a role in significantly changing their particle size. Average particle sizes of the as-prepared samples were 69.15 ± 14.47 nm, 68.33 ± 17.06 nm, 16.38 ± 4.02 nm and 27.00 ± 5.27 nm for 0 %, 1 %, 3 % and 5 % Er-doped ZnO samples, respectively. Raman spectra of the Er-doped ZnO samples were able to be used to identify the presence of defect and structural disorder in the ZnO lattice. The ZnO samples with and without Er dopant were tested for the degradation of methylene blue under visible light irradiation. Upon increasing the doped Er content, the degradation of methylene blue solution under visible light irradiation was enhanced. In this research, the 3 % Er-doped ZnO nanoparticles have the highest efficiency of 98.26 % under visible light irradiation within 100 min.

Integrating implants with the surrounding bone tissue is a significant challenge in medical engineering. A promising option with appropriate biological and mechanical characteristics is porous titanium, which can be employed in mineralizing bones and ingrowth applications. In the present study, titanium foams were fabricated using titanium hydride powder and the following space holders: (1) needle-shaped urea, (2) spherical urea, and (3) cubic sodium chloride. All samples were characterized by means of scanning electron microscopy with an energy-dispersive X-ray spectrometer, X-ray diffraction, and mechanical compression testing. Our results revealed that powder metallurgy is suitable for producing titanium foam with various pore morphologies. The shape of sample pores replicates the type of space holders. Also, the influence of three distinct pore morphologies on the human primary osteogenic sarcoma cell line, MG-63, was evaluated. In-vitro investigation showed that samples with sharp-cornered pores increase the attached cellular filopodia to the foams after seeding. This result is helpful in porous titanium applications for restoring bone defects.

In the present contribution, the age-hardening behavior of two commercial Al–Si–Cu–Mg alloys was studied during heat treatments at 200 °C and 240 °C. Size and volume fraction of precipitates were characterized by means of transmission electron microscopy, small-angle X-ray scattering, and small angle neutron scattering. Additionally, tensile tests were performed to evaluate the mechanical behavior. Finally, a multi-component multi-phase classical nucleation and growth theory precipitation model was developed to predict the evolution of Mg- and Cu-containing precipitates and their hardening effect. The simulations were in good agreement with experimental findings.

The microstructure, mechanical properties and corrosion resistance of friction stir welded joint of Al–Mg–Mn–Zr–Er alloy were investigated under three FSW parameter sets: 800 rpm × 100 mm min −1 , 800 rpm × 80 mm min −1 and 600 rpm × 80 mm min −1 . The microstructural transformation sequence of welded joint is discontinuous dynamic recrystallization, dislocation introduction, dynamic recovery and continuous dynamic recrystallization. The mechanical properties of welded joint are highly correlated with the welding process parameters. The welded joint can obtain good tensile strength and elongation under the parameters of 800 rpm × 100 mm min −1 . Corrosion resistance of welded joints has little correlation with welding parameters, but is mainly related to different positions of welded joints. The main influencing factor is grain structure state. The intergranular corrosion susceptibility is related to β(Al 3 Mg 2 ) phase.