High-temperature oxidation behavior of monolithic Zr3[Al(Si)]4C6 and its composite incorporating 30vol% ZrB2-SiC: Providing a basis for broadening the service temperature

To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr₃[Al(Si)]₄C₆ and a novel Zr₃[Al(Si)]₄C₆-ZrB₂-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr₃[Al(Si)]₄C₆ exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr₃[Al(Si)]₄C₆ exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B₂O₃ and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics.     

Influence of surfactants on rheological behaviors of polyacrylonitrile/dimethyl sulfoxide/silicon blending polymer solutions

KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability.     

首都体育馆改造中的可持续性措施

首都体育馆作为北京冬奥会的重要竞赛场馆,在改造过程中深入贯彻"绿色办奥"理念,采用二氧化碳制冰、LED照明、无障碍设施、新风系统、"海绵城市"等可持续性相关措施,为落成已经超过半个世纪的首都体育馆注入了新鲜的"绿色血液".     

浅议生态环境监测机构的风险控制

现阶段,为了探索创新性的发展途径,生态环境监测机构应始终增强风险控制意识。应加强风险管理,立足于风险控制,以求不断健康发展。     

The effect of alkali metal oxide on the properties of borosilicate fireproof glass: Structure,thermal properties,viscosity, chemical stability

The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R₂O–CaO–B₂O₃–SiO₂) systematically. Because the glass would emulsify when Li₂O was added to the glass batch, this article did not discuss Li₂O. The results showed that when the amount of Na₂O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na₂O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased.     

Nano-Al doped-MoO3 high-energy composite films with excellent hydrophobicity and thermal stability

Developing the thermal stability of metal-based ceramic composites or their films has always been challenging and bottlenecks for the utilization of energy. In this paper, the novel mesh-like functional Al doped-MoO₃ nanocomposite film with even distribution and high purity was firstly fabricated by the high-efficiency electrophoretic deposition and surface modification. The optimal suspension turned out to be the mixture of isopropanol and the additives of polyethyleneimine and benzoic acid. The microtopography, crystalline structure, environmental resistance and thermal stability were analyzed by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), exposure and droplet-impacting test, DSC analysis and ignition test, respectively. The water contact angle and sliding angle of product can reach ~170° and <1°, indicating the excellent anti-wetting property. In addition, the high heat-release (~3180 J/g) of product all kept almost unchangeable after six months exposure experiments, demonstrating the outstanding thermostability. The exquisite design idea here can perfectly match microelectromechanical system (MEMS), providing the valuable reference for fabricating other metal-based high-energy composites with long lifespan for real industrial applications.     

Microstructure and coloring mechanism of iron spots on bluish white porcelain from Jingdezhen of the Song Dynasty

Jingdezhen is famous for its bluish white (Qingbai) porcelains of the Song Dynasty, and those decorated with iron spots are distinctive among them. Herein, iron spots on a bluish white porcelain were investigated using a series of microscopic and spectroscopic characterizations. We found the decreasing iron content from more than 8 wt% to about 2 wt% during the glaze color transition from rusty to brown and finally into green, which built a connection on the coloring mechanism of iron-rich crystallized glaze and celadon glaze. We identified the rare ε-Fe₂O₃, a promising magnetic material, in both the dark brown crystals and the triangular crystals in the rusty area, which is its first discovery among bluish white porcelains. Based on these findings, we discussed the coloring mechanism of iron-spot decoration along with the physical form of the iron oxide crystals, indicating the partially reducing atmosphere during firing process.     

Self-healing,elastic and deformable novel composite phase change polymer based on thermoplastic elastomer SEBS for wearable devices

Journal of Materials Science - Form-stable composite phase change materials (C-PCMs) prepared by microencapsulation method and porous matrix adsorption method need for compression molding after...     

An Optimized Combination of Mine Water Control,Treatment, Utilization,and Reinjection for Environmentally Sustainable Mining: A Case Study

This paper presents a case study of an optimized combination of mine water control, treatment, utilization and reinjection to achieve the zero discharge of mine water. Mine water has been considered a hazard and pollution source during underground mining, so most mining enterprises directly discharge mine water to the surface after simple treatment, resulting in a serious waste of water. Moreover, discharging a large amount of mine water can destroy the original groundwater balance and cause serious environmental problems, such as surface subsidence, water resource reduction and contamination, and adverse impacts on biodiversity. The Zhongguan iron mine is in the major groundwater source area of the Hundred Springs of Xingtai, which is an area with a high risk of potential subsidence. To optimize the balance between mining and groundwater resources, a series of engineering measures was adopted by the Zhongguan iron mine to realize mine water control, treatment, utilization, and reinjection. The installation of a closed grout curtain has greatly reduced the water yield of deep stopes in the mine; the effective sealing efficiency reaches 80%. Nanofiltration membrane separation was adopted to treat the highly mineralized mine water; the quality of the produced water meets China’s recommended class II groundwater standard. Low-grade heat energy from the mine water is collected and utilized through a water-source heat pump system. Finally, zero mine water discharge is realized through mine water reinjection. This research provides a beneficial reference for mines with similar geological and hydrogeological conditions to achieve environmentally sustainable mining.