稀土复合作用下常温磷化工艺的研究

研究出一种含稀土和淀粉的常温磷化促进剂。探讨了稀土化合物、促进剂、磷化工艺参数如温度、时间和pH值对所得磷化膜外观、膜重和耐蚀性的影响。 结果表明：采用含稀土化合物的磷化促进剂,磷化膜的耐蚀性得到显著提高。     

Microstructure and corrosion behavior of in-situ grown Y3Si2C2 coated SiC fibers exposed to air and wet-oxygen at 1400 ℃

Y₃Si₂C₂ ternary ceramics were in-situ grown on the third-generation Chinese commercial SiC fiber (KD-SA SiC fiber) surface via molten salt method. Microstructures and oxidation/corrosion behavior of in-situ grown Y₃Si₂C₂ coated SiC fibers exposed to air and wet-oxygen at 1400 ℃ were investigated. Results indicated that the layered Y₃Si₂C₂ slices with thickness of approximately 15 nm can be successfully in-situ grown on SiC fibers. The product on the fibers surface after oxidation/corrosion at 1400 ℃ for 1 h in both ambient air and wet-oxygen are Y₂Si₂O₇ and SiO₂. Moreover, microstructural characterization indicates that the immigration and expansion of gaseous bubbles induced by oxidation product, mainly CO, result in microstructural differences of SiC fiber specimens, and finally oxidation mechanism based on the microstructural difference were proposed.     

Removal mechanism of SiC/SiC composites by underwater femtosecond laser ablation

Silicon carbide Ceramic matrix composites (SiC matrix with SiC fibers, abbreviated as SiC/SiC composites) are widely used in aerospace and energy applications due to their excellent resistance to high temperatures, corrosion, wear, and low density. However, the difficult machinability and surface oxidation of SiC/SiC composites are the main factors restricting their further application. To address these issues, this paper explores a novel method for underwater femtosecond laser ablation of SiC/SiC composites to obtain high cleanliness, low-oxidation microporous surfaces. This paper systematically analyses the changes in hole depth, material removal rate (MRR), surface morphology, and material components during underwater femtosecond laser ablation of SiC/SiC composites, and explains the formation of typical features such as induced cones, small banded pits, fiber debonding and shedding. Our work provides new research ideas for understanding the removal mechanism and surface oxidation resistance of SiC/SiC composites.     

改性纳米碳化硅/聚氨酯弹性体复合材料的制备

采用KH-560与KH-550反应得到新的硅烷偶联剂改性纳米碳化硅(SiC);再以2,4-甲苯二异氰酸酯(TDI)、聚氧化丙烯醚二醇(PPG2000)为原料合成预聚体,改性纳米SiC为填料、3,3’-二氯-4,4’-二氨基二苯甲烷(MOCA)为扩链剂,制备了改性纳米SiC/聚氨酯弹性体(PUE)复合材料。讨论了改性前后的纳米SiC添加量对复合材料的力学性能、耐磨性能和热稳定性的影响,并用扫描电镜分析了改性前后的纳米SiC在基体中的分散性。结果表明,改性后的纳米SiC在基体中的分散性优于纳米SiC,当改性纳米SiC质量分数为9%时,改性纳米SiC/PUE复合材料的力学性能达到最佳,耐磨性能明显改善,热失重温度提高了33℃。     

凝聚共沉法稀土掺杂高岭土/天然橡胶复合材料的性能研究

研究凝聚共沉法稀土掺杂高岭土/天然橡胶(NR)复合材料的性能,并与粉体高岭土/块状NR机械混炼硫化胶进行对比。结果表明:稀土掺杂高岭土在NR基体中具有良好的分散性,二者构成的界面结合牢固;与粉体高岭土/块状NR机械混炼硫化胶相比,凝聚共沉法稀土掺杂高岭土/NR硫化胶的拉伸强度、拉断伸长率和撕裂强度有较大提高;与镧和钐相比,镨化合物对高岭土的掺杂改性效果更明显。     

船舶热力管道的腐蚀与防护

对船舶热力管道的腐蚀原因及规律进行了分析,在对喷涂材料、蚀洗封孔涂料等方面进行研究的基础上,得出了“热喷涂稀土铝层 无机富锌蚀洗封孔涂层 耐高温面涂层”的复合涂层保护方案。     

碳化硅陶瓷的发展与应用

碳化硅陶瓷以其优异的抗热震、耐高温、抗氧化和耐化学腐蚀等特性而广泛地应用于石油、化学。汽车、机械和宇航等工业领域中,井日益引起人们的重视。本文对各种SIC陶瓷的制备方法、性能特点及其应用现状进行了综合评述。     

碳化硅陶瓷材料的制备工艺和应用研究进展

碳化硅陶瓷材料由于具有轻质高强、导热性能好、膨胀系数低、硬度高、抗氧化等优异的性能,被广泛用作高温结构部件。本文围绕碳化硅材料在光学反射镜材料的应用,对碳化硅材料的制备工艺和应用方面的进展作简要综述。     

国产连续碳化硅纤维的进展及应用

介绍了国产连续碳化硅（SiC）纤维的研究进展及国外连续碳化硅纤维产品的主要应用,展望了国内连续SiC纤维及其产品的发展趋势.表明SiC纤维具有高比强度、高比模量、耐高温、抗氧化、抗蠕变、耐化学腐蚀、耐盐雾和优良的电磁吸收特性,是耐高温陶瓷基复合材料的关键材料.     

碳化硅陶瓷的液相烧结及其研究进展

本文对碳化硅液相烧结添加系统及其烧结机理作了论述。有氧化物参与的碳化硅的液相烧结可以降低碳化硅的烧结温度，促进碳化硅的致密化，提高碳化硅陶瓷的性能。沿晶断裂和穿晶断裂混合断裂机理是液相烧结碳化硅陶瓷强度和韧性提高的原因，表面强化和韧化可以进一步提高碳化硅陶瓷材料的性能。     

The effect of rare earth oxides on the pressureless liquid phase sintering of α-SiC

Silicon carbide (SiC) ceramics have been fabricated by pressureless liquid phase sintering with Al₂O₃ and rare-earth oxides (Lu₂O₃, Er₂O₃ and CeO₂) as sintering additives. The effect was investigated of the different types of rare earth oxides on the mechanical property, thermal conductivity and microstructure of pressureless liquid phase sintered SiC ceramics. The room temperature mechanical properties of the ceramics were affected by the type of rare earth oxides. The high temperature performances of the ceramics were influenced by the triple junction grain boundary phases. With well crystallized triple junction grain boundary phase, the SiC ceramic with Al₂O₃–Lu₂O₃ as sintering additive showed good high temperature (1300 °C) performance. With clean SiC grain boundary, the SiC ceramic with Al₂O₃–CeO₂ as sintering additive showed good room temperature thermal conductivity. By using appropriate rare earth oxide, targeted tailoring of the demanding properties of pressureless liquid phase sintered SiC ceramics can be achieved.     

Interactions of Na2SO4 and yttrium-silicate environmental barrier coatings at 825°C

Yttrium-silicates (Y₂Si₂O₇ and Y₂SiO₅) are candidate environmental barrier coating (EBC) materials for silicon carbide ceramic matrix composites (SiC-CMCs). These materials’ high-temperature, high-velocity steam, and siliceous debris resistance are well studied. However, Na₂SO₄-induced hot corrosion mechanisms are less understood. Free-standing atmospheric plasma sprayed Y₂Si₂O₇ and Y₂SiO₅ coupons were exposed to 2.5 mg/cm² of Na₂SO₄ at 825°C in 0.1% SO₂-O₂ (g). Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry were used to identify a previously unknown damage mechanism. Water-soluble Y and Na-Y sulfates and oxysulfates formed in reaction with Na₂SO₄, causing significant damage to the yttrium-silicate EBCs materials.     

Influence of rare earth Y on the corrosion behavior of as-cast AZ91 alloy

The influence of different contents of rare earth Y on the corrosion resistance of AZ91 alloy was investigated by the salt spray test and electrochemical measurements. It was found that the proper amount of Y was effective on improving the corrosion resistance of AZ91 alloy. The optimal modification effect was obtained when the Y content in the alloys was 0.3 wt.%. However, with the increase of rare earth Y, the corrosion rate became bigger slightly, and further addition of Y content over 0.3 wt.% resulted in the increment of the corrosion rate. It is suggested that the excessive rare earth Y can reduce the corrosion resistance of AZ91 alloy.     

抗氧化耐磨蚀复合SiC材料的研究及应用

研究试验了稀土氧化物，A、B添加物及硅线石的加入量对碳化硅－硅线石复合材料性能的影响。结果表明：引入适量的稀土氧化物能改善材料的抗氧化性及抗侵蚀性，氧化速度比粘土结合SiC降低十余倍；采用A、B添加剂能提高材料的基质密度、抗折强度及耐磨性能，基质强度可达100MPa以上；适量的硅线石使材料的抗热震性明显提高。用该材料做的分离器叶片，满足了循环流化床锅炉内恶劣环境中长期使用的要求。     

Corrosion of silicon carbide hot gas filter candles in gasification environment

Reliable cleaning of the fuel gas is required to meet the environmental regulations and to prevent corrosion and erosion of downstream components. The aggressive process environment in biomass-gasification power generation systems or in biofuels production systems can cause corrosion in ceramic hot gas filter candles used to clean the fuel gas. Therefore, to improve the reliability and durability of filters, the influence of steam, ash, and alkaline (earth) metals on the corrosion processes was studied for silicon carbide filter candles fabricated by Pall Schumacher. Exposures with biomass and lignite ashes caused a macroscopically expansion as well as microstructural effects that were analysed by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. All effects are discussed and it is shown that the employment of silicon carbide filter candles in water vapour containing, alkali-rich gasification environment at high temperature is problematic.     

Preparation of aluminum/silicon carbide metal matrix composites using centrifugal atomization

This paper describes the development of a new technique to produce metal matrix composites (MMCs) by injecting silicon carbide particles into molten aluminum just prior to centrifugal atomization. A centrifugal atomization apparatus has been constructed for this study. Silicon carbide particles are injected during atomization of 6061 aluminum alloy to form metal matrix composite powder. The prepared aluminum/silicon carbide powder contains 18 vol.% of SiC particles and 1.2 vol.% of voids. The particle grain size is almost independent from the particle size.     

锌及镀锌层稀土转化膜研究进展

锌及镀锌层表面稀土转化膜具有良好的耐蚀性能和无毒、无污染等优点,是最有希望替代铬酸盐处理的转化膜之一,具有良好的发展前景.本文综述了国内外关于锌及镀锌层上单一稀土转化膜的成膜工艺及其机理,并概述了国内外稀土复合膜的研究成果.     

氧化锆-碳化硅复合材料性能研究

从稀土氧化物、氧化锆含量、碳化硅含量、温度及制备工艺方面对氧化锆-碳化硅复合材料电阻率的影响进行了讨论,同时探讨了氧化锆-碳化硅复合材料的高温氧化性能,为氧化锆-碳化硅复合材料的制备及其电性能研究提供了依据。     

Enhanced electromagnetic microwave absorption of SiC nanowire-reinforced PDC-SiC ceramics catalysed by rare earth

Rare earth elements can modulate the dielectric constant of materials and significantly improve their dielectric properties. Herein, SiCnws/SiC ceramics were prepared through polymer derived ceramics (PDCs) technology with rare earth Sc particles as the catalyst. The Sc particles promote the precipitation of SiC and C from the matrix. Furthermore, the SiCnws, grown via the vapour-liquid-solid (VLS) mechanism, construct the three dimensional (3D) network structure to improve impedance matching and loss characteristics. Remarkably, the SiCnws/SiC ceramics minimum reflection coefficient (RC_min) achieved a value of ?33.2 dB at 9.4 GHz with a thickness of 2.75 mm, and the effective absorption bandwidth (EAB) was 4.2 GHz covering the whole X band. When microwaves permeated into the SiCnws/SiC ceramics, those trapped in the 3D network structure underwent a variety of microwave energy dissipation processes, including multiple reflections, scattering, and interface and dipole polarisation. Consequently, SiCnws-reinforced PDC-SiC ceramics catalysed by rare earth emerge as a promising new approach to enhance electromagnetic (EM) wave absorption performance.     

A focused review on the tribological behavior of C/SiC composites: Present status and future prospects

Silicon carbide-based ceramic matrix composites have received extensive attention in recent years. Many excellent reviews have reported on the tribological behavior of carbon fiber-reinforced carbon and silicon carbide dual matrix (C/C-SiC) composites. However, a systematic overview of the tribological properties of carbon fiber-reinforced silicon carbide (C/SiC) composites does not exist. This review focuses on C/SiC composites and summarizes the key factors, including internal factors (constituent content, graphitization process, material structure and fiber direction), and various test conditions (pressure and speed, dry and wet, temperature, and counterparts) that affect their tribological behavior. Their wear mechanisms under different conditions are elaborated. Finally, some potential future development directions for improving the performance of C/SiC composites are proposed to provide high-quality ceramic matrix composites for engineering applications. These directions include structural modification, matrix modification, coating technology, laser surface texturing, and material genome method.