Channel: Engineering and Technology http://pmbjb.csu.edu.cn EN-US http://pmbjb.csu.edu.cn/EN/current.shtml http://pmbjb.csu.edu.cn 5 2O₃ was selected as a mineralizer for the preparation of silica based ceramic cores used in precision casting. Techniques such as X-ray diffractometer, field emission scanning electron microscope, energy dispersive spectroscopy, and the three-point bending testing were employed to investigate the effects of mineralizer amount and silica sol strengthening treatment on the phase composition, microstructures, shrinkage rate, open porosity, density, and bending strength of the ceramic cores. The results indicate that α-Al₂O₃ exerts a dual effect on the ceramic cores. On one hand, it acts as a reinforcing phase that hinders the viscous flow of fused quartz and enhances the strength of the cores; on the other hand, its excellent high-temperature stability reduces the sintering density of the ceramic cores, leading to decreased shrinkage rates and strength. However, silica sol strengthening treatment effectively seals the pores and promotes sintering of the cores. After silica sol strengthening treatment, cores with w(α-Al₂O₃)=2% exhibit an increase in room temperature bending strength to 16.6 MPa and high-temperature bending strength to 37.5 MPa, meeting the application standards for ceramic cores in the precision casting industry.]]> φ(Ni)=2% have the best laminar structure characteristics, the thermal conductivity of the composite is 2.24 W/(m·K), and the thermal expansion coefficient is 30.23×10^-6 K^-1.]]> 3 and Dy₂O₃ powders were used as diffusion sources to prepare high Ce content (Pr,Nd)₂₀Ce₁₁Fe_bal(Cu,Ga,Zr)_1.0B_0.97 (mass fraction) sintered magnets. The effects of DyF₃/Dy₂O₃ co-diffusion on the magnetic properties and microstructure of the magnets were investigated using ultra-high coercivity permanent magnet pulsed field magnetometer, X-ray diffractometer, differential scanning calorimeter, and electron probe microanalyzer. The results show that after DyF₃/Dy₂O₃ diffusion, the coercivity increases from 913.01 kA/m to 1 237.78 kA/m, representing an enhancement of 324.77 kA/m (35.6%). Additionally, the thermal stability is improved as the temperature coefficient of coercivity increasing from -0.606 %/℃ to -0.567 %/℃ in 20-120 ℃. The variation in remanence is minimal, with a change of only -0.01 T. After diffusion, the surface layer of the magnet predominantly consisted of the tetragonal (Nd,Ce,Dy)₂Fe₁₄B primary phase, along with a small proportion of cubic RE-O-F secondary phase. In the DyF₃/Dy₂O₃ system, Dy₂O₃ reduces the decomposition temperature of DyF₃ (<600 ℃), thereby providing a driving force for the diffusion of Dy atoms. Dy diffusion depth in DyF₃/Dy₂O₃ co-diffusion reaches up to 800 μm, the content of Dy gradually decreases with the increase of diffusion depth. Enriched regions of Dy and F elements are observed in the surface layer (0-60 μm). Ce is primarily enriched in the 0-60 μm range and at the triangular grain boundaries inside the bulk of the magnet. At a depth of 50-400 μm from the surface, Dy elements form a continuous network-like (Nd,Ce,Dy)₂Fe₁₄B shell structure around the main phase grains, which can effectively enhance the magnetocrystalline anisotropy field at the main phase grain surfaces, suppress the nucleation of reverse magnetization domains at the grain surfaces, and consequently improve the coercivity.]]> 2 atmosphere to produce SiC(O) fibers, then the microstructures and oxidation resistance of the SiC(O) fibers were investigated. The results show that the SiC(O) fibers exhibit a diameter of 200-300 nm, excellent uniformity, and pore-free surface. Moreover, their oxidation resistance at 600 ℃ surpasses that of carbon fibers.]]> 2 into chemicals with added value through electrocatalysis is an effective solution for reducing atmospheric CO₂ concentration and alleviating the energy crisis. In this paper, the effects of adding phosphoric acid on the microscopic morphology and electrocatalytic CO₂ reduction properties of CuS micro/nano-tubes were investigated by X-ray diffractometer, scanning electron microscope, transmission electron microscope, and electrochemical experiments. The results show that the addition of phosphoric acid leads to shorter lengths, smaller outer diameters, and thinner constituent unit nanosheets of micro/nano-tubes. The reduced micro/nano-tube size helps to expose more active sites, which improves the electrocatalytic CO₂ reduction properties with a Faraday efficiency of the liquid-phase product formic acid up to 68% at -1.0 V. This work is expected to provide guidance for the design and preparation of catalysts for electrocatalytic CO₂ reduction.]]>