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151.
Sufang He Zhanqiang Mei Nengsheng Liu Lei Zhang Jichang Lu Xiaofeng Li Jing Wang Dedong He Yongming Luo 《International Journal of Hydrogen Energy》2017,42(21):14429-14438
The effect of nickel precursor on Ni/SBA-15 catalysts was studied in ethanol steam reforming (ESR) for hydrogen production. These catalysts were prepared via incipient-wetness impregnation method using nickel nitrate and nickel citrate precursors, respectively (denoted as Ni/SBA-15(N) and Ni/SBA-15(C), respectively), and characterized by various techniques including H2-TPR, XRD, TEM and TG. It was found that the use of nickel citrate precursor, compared to nickel nitrate precursor, could greatly strengthen the NiO-support interaction and promote the homogeneous distribution of nickel species, to obtain the small nickel particles with high dispersion. After a 25 h time-on-stream test, much lower coke deposition was formed over Ni/SBA-15(C) than Ni/SBA-15(N). Moreover, NiCx species had be found over the used Ni/SBA-15(C), in which the carbon could be removed easily at lower temperature to exposure the active Ni sites; While carbon nanofibers with regular graphite-structure were the primary coke species over the spent Ni/SBA-15(N), which was difficultly remove and thus covered the active Ni sites easily. Due to these, Ni/SBA-15(C) displayed the higher catalytic activities and better stabilities in ESR than Ni/SBA-15(N). In summary, nickel citrate is an excellent precursor for the preparation of Ni/SBA-15 catalysts with high dispersion and strong interaction. 相似文献
152.
Jianqiao Yang Shuzhong Wang Donghai Xu Yang Guo Chuang Yang Yanhui Li 《International Journal of Hydrogen Energy》2017,42(31):19788-19797
The corrosion behavior of 316 SS and three Ni-based alloys 625, 600 and 800 was evaluated by exposing in SCW at 400 °C and 24 MPa with 6000 ppm NH4Cl for 70 h. Various of analytical techniques were used for corrosion analysis. 316 SS underwent severe corrosion attack for general corrosion, pitting corrosion and intergranular attack. Inconel 625 showed the best corrosion resistance in the test environment. Fe oxides and spinel were identified by XRD on all of the SCW-exposed samples. Trace amounts of NiO was also identified on the surface of samples, however, Ni was selectively dissolved and depleted in oxide films, and nickel ammine may form at the relatively low temperature during the heating and cooling process. 相似文献
153.
采用激光熔覆工艺在TC4钛合金基体表面制备了添加不同质量分数(0%、2%、4%、6%)TiC的Ni60A复合熔覆层,通过光学显微镜、显微硬度计、X射线衍射仪、摩擦磨损机分析了不同TiC含量对熔覆层组织及性能的影响。结果表明:未添加TiC的熔覆层组织以树枝晶为主,添加TiC后出现了花瓣状物相;XRD分析发现熔覆层中出现了AlCCr2、Al0.24B0.01Ni0.75等硬质增强相,这些能够显著提高熔覆层的硬度。显微硬度及摩擦磨损试验结果表明,添加TiC的熔覆层平均硬度均较基体硬度有大幅提高,摩擦因数显著降低,且随TiC含量的增加,熔覆层硬度先增加后降低,摩擦因数先降低后增加,4%TiC熔覆层的硬度最大,相比基体提高了213.3%,摩擦因数最小,为0.309 774。 相似文献
154.
Wei Song Xin-Guang Wang Jin-Guo Li Ye-Shun Huang Jie Meng Yan-Hong Yang Jin-Lai Liu Ji-De Liu Yi-Zhou Zhou Xiao-Feng Sun 《金属学报(英文版)》2020,33(12):1689-1698
Two experimental alloys containing different contents of Ru were investigated to study the effect of Ru on the microstructural evolution during long-term thermal exposure. The increase in Ru promoted the formation of cubical, tiny, and even γ′ phase after full heat treatment. Moreover, the samples after full heat treatment were exposed at 1100 °C for different time. Based on the classical model by Lifshitz, Slyozov, and Wagner, the coarsening of γ′ phase of the alloy containing 2.5 and 3.5 wt.% Ru during the long-term aging was controlled by the interface reaction and diffusion, respectively. The γ/γ′ lattice misfit was more negative with the increment of Ru addition, which induced the formation of stable rafted γ′ phase in the alloy containing 3.5 wt.% Ru at the initiation of long-term aging. Besides, the increase in Ru reduced the diffusion coefficient, which could restrain the γ′ phase coarsening. The lower γ/γ′ lattice misfit of the alloy containing 2.5 wt.% Ru promoted the interface reaction, which induced the rapid coarsening of γ′ phase. Therefore, the increase in Ru improved the microstructural stability of the alloys. On the other hand, the raise of Ru induced “reverse partitioning” behavior, which was effective in suppressing the emergence of the topologically close-packed phase (TCP phase). The TCP phase occasionally occurred in the alloy containing 2.5 wt.% Ru, which was attributed to the high temperature and the supersaturation of the γ matrix. Moreover, the TCP phase was determined as μ phase, which had a high concentration of Co, Re, Mo, and W. A sketch map describing the evolution of the TCP phase was also constructed. 相似文献
155.
针对镍基高温合金因加工硬化严重成形时极易产生破裂和起皱等典型缺陷的问题,以锥筒形壳体类零件为对象,提出了一种由锥形预制坯经过真空固溶处理后拉深旋压成形锥筒形件的方法,并对其成形机理进行了研究。基于Abaqus/Explicit平台,建立了锥筒形件拉深旋压有限元模型,分析了成形过程中的瞬态等效应力、等效塑性应变、切向应力、壁厚及三向应变分布规律。结果表明:在旋压成形过程中,最大瞬态等效应力位于旋轮接触区及附近区域、最大瞬态等效塑性应变位于坯料口部;瞬态切向压应力最大值位于旋轮接触区,而瞬态切向拉应力最大值位于旋轮接触区附近的两侧区域。筒形段中部壁厚减薄,而坯料口部壁厚增厚。旋压成形试验表明,锥形预制坯经拉深旋压后可获得壁厚均匀的锥筒形件。 相似文献
156.
《中国有色金属学会会刊》2020,30(8):2143-2155
The influence of brazing temperature and brazing time on the microstructure and shear strength of γ-TiAl/GH536 joints brazed with Ti−Zr−Cu−Ni−Fe−Co−Mo filler was investigated using SEM, EDS, XRD and universal testing machine. Results show that all the brazed joints mainly consist of four reaction layers regardless of the brazing temperature and brazing time. The thickness of the brazed seam and the average shear strength of the joint increase firstly and then decrease with brazing temperature in the range of 1090−1170 °C and brazing time varying from 0 to 20 min. The maximum shear strength of 262 MPa is obtained at 1150 °C for 10 min. The brittle Al3NiTi2 and TiNi3 intermetallics are the main controlling factors for the crack generation and deterioration of joint strength. The fracture surface is characterized as typical cleavage fracture and it mainly consists of massive brittle Al3NiTi2 intermetallics. 相似文献
157.
采用5 kW CO2激光器在低碳钢表面熔覆Ni基合金层及TiB2/Ni基合金金属陶瓷涂层,研究了两种涂层的组织、显微硬度以及滑动磨损特性.结果表明,Ni基合金层主要组成相为γ-(Ni,Fe),Cr23C6等,TiB2/Ni基合金复合涂层组成相主要有γ-(Ni,Fe),Ni3B,TiB2和TiC等;Ni基合金层由发达γ-(Ni,Fe)枝晶和其间共晶组织所组成,TiB2/Ni基合金复合涂层典型组织为等轴固溶体以及其间细小共晶组织;TiB2对熔覆层的组织有显著的影响,使熔覆层组织细化,并由树枝晶转变为等轴晶;加入TiB2可显著提高Ni基合金涂层的显微硬度及耐磨性能. 相似文献
158.
Ni对TiC-Ni超音速火焰喷涂层组织和耐磨性的影响 总被引:2,自引:1,他引:1
Ni对Ti-Ni-C体系SHS反应中的热力学与动力学均有重要影响,Ni在超音速火焰喷涂合成中的作用尚不明确.利用超音速火焰喷涂合成技术制备了3种不同Ni含量的TiC-Ni金属陶瓷涂层,并对涂层进行了组织和性能研究.结果表明,Ni在喷涂过程中起到了吸收反应热、减缓喷涂合成过程中粉末组分的氧化、并在涂层中黏结相金属的作用.原料中的Ni含量对涂层的组织和性能影响较大,Ni含量低涂层中含有大量氧化物,且组织疏松、滑动磨损性能差;随着Ni含量升高到40%时,涂层的氧化物含量降低,滑动磨损性能增强; Ni含量过高,涂层中Ni片层增多,硬质相间距加大,涂层的耐磨损性能有所降低. 相似文献
159.
用HGL-6000型横流CO2激光器在316L不锈钢表面熔覆Ni-WC涂层。采用金相显微镜观察熔覆层组织形貌;利用显微硬度计和电化学工作站研究了不同激光功率对熔覆层硬度及耐蚀性的影响。结果表明,熔覆层组织主要为树枝晶及共晶组织自表面向内部逐渐粗化;随激光功率增加,熔覆层组织先细小后变得粗大,当激光功率为3500 W时,组织最细小;随功率增加,熔覆层硬度降低,且自表面至结合处均呈下降趋势,当激光功率为2500 W时,熔覆层硬度(573HV1)最高,为基体的3.3倍,功率为3500 W时,熔覆层硬度为基体的2.2倍;随功率增加,熔覆层耐蚀性先增强后减弱,功率为3500 W的熔覆层耐蚀性优于其它功率的熔覆层且与316L不锈钢耐蚀性相当。 相似文献
160.
氩气气氛保护下采用气压烧结技术制备掺杂Y2O3的17Ni/(NiFe2O4-10NiO)金属陶瓷惰性阳极,在电解温度(960℃)下,对材料进行抗高温氧化性能研究.采用SEM分析材料及氧化产物的各物相分布情况、氧化形貌,并利用XRD进行成分分析.结果表明,金属陶瓷阳极的氧化动力曲线均大致符合抛物线规律;掺杂适量的Y2 O3对金属相的分散有一定作用,并能有效抑制烧结试样及氧化物的孔洞生成,从而显著改善该金属陶瓷的抗高温氧化性能,其中,当Y2 O3掺杂量为0.5%时,材料抗高温氧化性能最好,30 h后单位面积氧化增重量仅为10.6591 mg/cm2. 相似文献