High stability superhydrophobic glass-ceramic surface with micro–nano hierarchical structure

Inspired by the surface structure of lotus leaves, micro–nano hierarchical surface structures have been widely used for designing superhydrophobic surfaces. However, the conventionally designed superhydrophobic surface structures are fragile. In this study, a layer of micron-sized mullite whiskers was grown using molten salt on the surface of BaAl₂Si₂O₈ (BAS) glass ceramics. Subsquently, SiO₂ nanoparticles modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane were sprayed onto the whisker layer to form a superhydrophobic surface. The nanoparticles exhibit superhydrophobicity, which is protected by the whisker layer containing pores and bulges. This prohibits direct contact between the nanoparticles and external objects. Contact and rolling angle tests indicated that the surface contact angle of the micro–nano hierarchical structure is 158° and the rolling angle is less than 10°. The stability of the superhydrophobic surface was tested through ultraviolet light, long-time immersion in solutions with various pH values, water scouring, and sandpaper abrasion. The results showed that the contact angle is greater than 150°. This study is expected to provide a simple and effective method for fabricating superhydrophobic surfaces on ceramics on a large scale.     

Optimizing the stability and electrical transport properties of CeNbO4+δ-based oxide ceramics by regulating oxygen ion content

CeNbO_4+δ ceramics have attracted extensive research interest because of their unique mixed ion-electron transport characteristics and interesting structure-functional characteristics caused by the difference in oxygen ion content. Although the change of oxygen ion content brings rich redox properties, it also causes serious crystal transformation and abnormal electrical transport properties. In order to obtain stable structure and excellent electrical transport properties, the directional regulation of the oxygen ion content has been realized through introducing Al₂O₃ and high temperature aging. After 600 h of aging at 1073 K, the prepared composite ceramics not only obtain a stable structure without crystal transformation, but also show good negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K–1273 K, in which the linear fitting maximum Pearson's r of the relationship between lnρ and 1000/T can reach 99.97%. The proposed method provides a new thought for the design and application of high-temperature electronic ceramics.     

(1-x)Bi0.5Na0.47Li0.03TiO3-xNaNbO3 lead-free ceramics with superior energy storage performances and good temperature stability

Dielectric capacitors show great potential in superior energy storage devices. However, the energy density of these capacitors is still inadequate to meet the requirement of energy storage applications. In this study, the Bi_0.5Na_0.47Li_0.03TiO₃-xNaNbO₃ (BNLT-xNN) ceramics were prepared via conventional solid-phase reaction. Results showed that NN can efficaciously enhance the breakdown strength (E_b) and the relaxation behavior of the BNLT ceramic because of the broken ferroelectric long-range order. When x = 0.3, the maximum E_b reached 350 kV/cm, at which the 0.7BNLT-0.3NN ceramic exhibited the high recoverable energy storage density (W_rec) of 4.83 J/cm³ and great efficiency (η) of 78.9%. The ceramic demonstrated good temperature stability at 20 °C-160 °C and excellent fatigue resistance. Additionally, the 0.7BNLT-0.3NN ceramic presented high power density (P_D; ～77.58 MW/cm³), large current density (C_D; ～861.99 A/cm²), and quite short discharge time (t_0.9; ～0.090 μs). These results indicated that the 0.7BNLT-0.3NN material has excellent energy storage properties and various application prospects.     

Impact of high-intensity ultrasound on physical properties and degree of oxidation of lipase modified menhaden oil with caprylic acid and/or stearic acid

The purpose of this research was to determine the effect of high-intensity ultrasound (HIU) on physical properties, degree of oxidation, and oxidative stability of structured lipids (SLs). Caprylic acid (C) and stearic acid (S) were incorporated into menhaden oil using Lipozyme® 435 lipase to obtain five samples: (1) LC 20 (menhaden oil with 20% of C), (2) LC 30 (menhaden oil with 30% C), (3) LS 20 (menhaden oil with 20% S), (4) LS 30 (menhaden oil with 30% S), and (5) Blend C (menhaden oil with 16.24% C and 13.04% S). Samples were crystallized for 90 min at the following temperatures: (1) LC 20 at 15.5°C, (2) LC 30 at 17.5°C, (3) LS 20 at 24°C, (4) LS 30 at 30°C, and (5) Blend C at 18.0°C, and HIU was applied at the onset of crystallization. Physical properties, degree of oxidation, and oxidative stability were evaluated in sonicated and nonsonicated samples. All SLs had statistically higher G′ after sonication. Sonicated LS 30, LC 30, and Blend C had a higher melting enthalpy than the nonsonicated ones, while enthalpy values in sonicated LS 20 and LC 20 samples were not statistically different than the nonsonicated ones. No significant difference between sonicated and nonsonicated samples was observed in peroxide values (1.2 ± 0.1 meq/kg, p > 0.05) and in the oxidative stability index (6.3 ± 0.2 h, p > 0.05). These results showed that HIU was effective at changing physical properties without affecting the oxidation of the samples.     

Meticulously tailoring phase boundary in KNN-based ceramics to enhance piezoelectricity and temperature stability

Although KNN-based ceramics with high electrical properties are obtained through a variety of strategies, the temperature sensitivity is still one of the key technical bottlenecks hindering practical applications. Here, we use a new strategy, meticulously tailoring phase boundary, to refine the ferroelectric boundary of KNN-based ceramics, leading to high piezoelectricity companied with improving temperature stability. The highest d₃₃ value in this system reaches 501 pC/N with a T_C ∼ 240°C, whereas a large strain of ∼0.134% can be kept with 10% lower deterioration until 100°C. The origin of high piezoelectricity is mainly attributed to the well-preserved multiphase coexistence and the appearance of nanodomains, which greatly facilitate the polarization rotation. Instead of the changed intrinsic thermal insensitivity, the precision phase boundary engineering plays an important role in strengthening the temperature stability of electric-induced strain. This work provides a simple and effective method to obtain both high electrical properties and excellent thermal stability in KNN-based ceramics, which is expected to promote the practical applications in the future.     

高应力软岩巷道锚注一体化联合支护技术应用

介绍了国家专利注锚剂、中空注浆锚索等产品,以国家能源麦朵山煤矿11采区2煤辅助运输巷为研究对象,采用数值模拟、理论分析、现场测试及井下试验相结合的综合研究方法,对11采区2煤辅助运输巷采用锚注一体联合支护技术,来实现对岩体裂隙注浆,使浆料与岩体结为一体,在围岩与支护体共同作用过程中,实现强岩增荷的作用,维护巷道的稳定性,实现工作面的安全生产。     

Thermal stability of C/Mullite composites in different environments

In the present study, the mechanical properties and microstructure of C/Mullite composites with a PyC-SiC double-layer interfacial coating after annealing were systematically studied to evaluate the evolution of thermal stability in an inert atmosphere and a vacuum. The C/Mullite composites annealed in the inert atmosphere exhibited better thermal stability than those annealed under the vacuum. The main factor for failure of the composites was carbothermal reduction. The activation temperature of carbothermal reduction in composites in the inert atmosphere was ～100 °C higher than that in the vacuum. Once carbothermal reduction was activated, the microstructure of composites was destroyed, resulting in a significant weight loss and mechanical property degeneration. The degeneration of mechanical properties was unrecoverable.     

Revealing the dimensional stability mechanisms of SiC/Al composite under long-term thermal cycling

Long-term thermal cycling causes irreversible dimensional changes of the material, which in turn affects the reliability of precision instruments. In this paper, dimensional stability mechanisms of SiC/Al composites during thermal cycling were revealed using high-precision thermal dilatometer, XRD and spherical aberration correction transmission electron microscope (Cs-TEM). First, how the factors including dislocations, internal stress and precipitates affect the dimensional change of SiC/Al composites were separately introduced. Then, the integrated effect of these factors affecting the dimensional stability of SiC/Al composites was further discussed. Among them, the integrated effect of dislocation-internal stress in SiC/pure Al composites leads to an increase in dislocation density and average lattice constant, which leads to an increase in dimensional change. The integrated effect of dislocation-internal stress-precipitates in SiC/2024Al composites leads to a decrease in the average lattice constant and some changes in the precipitation behavior (including the type, density and lattice constant of the precipitates), which ultimately leads to a decrease in dimensional change. The dimensional change of the two types of composites was semi-quantitatively estimated. Finally, the reasons for the significantly higher dimensional stability of the SiC/2024Al composites were given.     

蒸压建材生产过程中钢渣安定性处理与活性化利用

钢渣安定性处理过程常常造成胶凝活性的损失。为此，本文利用改性助剂消除钢渣水化过程中产生的氢氧化物并生成胶凝产物，在蒸压建材的生产过程中实现钢渣安定性处理和游离氧化物的活性化利用，并避免单独处置钢渣造成的活性物质损失。研究表明，8%秸秆灰和3%磷酸二氢铵作为复合助剂制备的尾矿-钢渣蒸压试块体积稳定，抗压强度达24.0MPa。通过对蒸压样品游离氧化物消解率、化学结合水量及热重、XRD分析，得出钢渣安定性处理与活性化利用机制：硅质材料与钢渣中f-CaO水化生成的Ca(OH)₂结合迅速生成对体系力学强度有益的水化硅酸钙，避免因大量Ca(OH)₂积累造成体积膨胀；磷酸盐中的NH₄⁺、H₂PO₄^-与f-MgO结合生成磷酸铵镁及其他低溶度积复盐类矿物，进而消除因f-MgO水化生成Mg(OH)₂造成体积膨胀的隐患。试样在180℃蒸压4h后，f-CaO及f-MgO消解率分别可达86.28%、89.73%。本文将为利用钢渣大比例取代水泥和石灰生产蒸压建筑材料提供理论基础，对于提高钢渣利用率、减少碳排放具有重要价值。     

Behaviour of 54.4SiO2-13.7Na2O-1.7K2O-5.0CaO-12.4MgO-0.6Y2O3-11.3Al2O3-0.9B2O3 HT-SOFC glass sealant under oxidising and reducing atmospheres

The behaviour of the promising glass sealant 54.4SiO₂-13.7Na₂O-1.7K₂O-5.0CaO-12.4MgO-0.6Y₂O₃-11.3Al₂O₃-0.9B₂O₃ for solid oxide fuel cells (SOFCs) under SOFC operating conditions was studied. First, the kinetics of the crystallisation processes at the operating temperature (850 °C) was discussed (maximum exposure time of 1000 h), and the effect of crystallisation on the coefficient of thermal expansion (CTE) of the sealant was studied. Furthermore, the degradation processes at the interface of the glass sealant and functional SOFC materials (Crofer 22 APU, YSZ, and NiO(Ni)-YSZ) during exposure to 850 °C in oxidising and reducing atmospheres for 500 h were studied. The tests demonstrated good performance of the sealant studied and possibility of its application in SOFCs.