Modelling diffusion-controlled kinetics in equilibrium and driven alloys

Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori.     

纳米Fe-Cu体系的结构和电阻温度特性

采用机械合金化方法制备了亚稳Fe50Cu50纳米合金粉末,压片后在氩气中分别进行523 K、873 K热处理。利用X-ray衍射和M ssbauer效应对样品的结构和相变进行了分析,结果表明,机械合金化后的样品为面心立方结构的固溶体,经523K热处理后,亚稳合金已开始分解;经873 K热处理后,样品已完全转变为纳米尺寸的α-Fe和Cu的混合体。在15~295 K内对热处理后样品的电阻进行了测量,结果表明,样品表现为负的电阻温度系数。     

Metallurgical slag properties as a support material for bimetallic nanoparticles and their use in the removal of malachite green dye

Fe-Cu oxides nanoparticles (Nps) were embedded in two steel slag wastes (SSB and SSW) to develop SSB/Fe-Cu and SSW/Fe-Cu nanocomposites. Nps with mean sizes between 10–20 and 6–10 nm on SSW and SSB, respectively are agglomeration with a different shape. Their characteristics were investigated by XRD, TEM, BET, SEM techniques. The Nps modified the morphology of both support materials. XRD pointed out the presence of Cu and Fe. The proportion of Cu concentration was higher than the one of Fe. Nanocomposites were tested in malachite green removal from aqueous solution. The adsorption kinetic indicated physisorption and chemisorption as the main mechanisms of adsorption. The adsorption capacities were 88.26 and 63.55 mg/g for SSW/Fe-Cu and SSB/Fe-Cu, respectively. This novel, easy to prepare and low-cost nanocomposites is an efficient adsorbent material. The presence of calcium compounds may improve Nps deposition an MG removal. Materials with ferric phases are not as efficient as the first one; Fe is not well supported on the material. The removal of MG took place by dye structure modification and by interactions with Cu nanoparticles improving the oxidation-reduction process, through synergic effects.     

Characterization of fused Fe-Cu based catalyst for higher alcohols synthesis and DRIFTS investigation of TPSR

Fused Fe-Cu based catalyst for higher alcohols synthesis (HAS) is characterized by XRD, TG-DTA, H₂-TPD and DRIFTS of CO adsorption. The results of XRD reveal that the fused Fe-Cu based catalyst consists of Cu₂O, CuFeO₂ and CuFe₂O₄ species. After reduction, the metallic Fe and Cu are the main species, but minor CuFeO₂ and CuFe₂O₄ species are also present. H₂-TPD shows that in comparison with the pure Fe- or Cu-based sample, the ability of Fe-Cu based catalyst for activation of H₂ is higher and the stronger metal-hydrogen bonds are formed. DRIFTS of CO adsorption indicates that CO is adsorbed on both metal and metal ion sites, where the dissociation of CO to C* and O* species and the formation of CO₂ are observed. In situ DRIFTS investigation of CO + H₂-TPSR over the Fe-Cu based catalyst shows that the dissociative activation of H₂ is more difficult than the activation of CO, and carbonaceous and hydrocarbon fragment species only appears after the dissociative activation of H₂. In addition, HAS over the Fe-Cu based catalyst is very complicated, where various intermediates including = CH₂, − CHO, − OOCH, − OH and − C(= O)-R exist.     

Fe-Cu 超饱和固溶体的机械合金化合成

采用 X 射线衍射,电子衍射等方法,对不同成分的 Fe-Cu 二元混合物粉末经不同研磨时间的结构进行了测定、分析。结果表明,在高能球磨条件下,原本在固态下溶解度极低的 Fe-Cu 系列的溶解度大为提高,其面心立方结构一直可维持到60at.-%Fe。     

金刚石工具专用电沉积铁铜合金的研制

采用双阳极动态阴极电解槽以电沉积的方式制备铁铜合金Fe70Cu30,通过工艺试验、添加试验测定铁铜合金的性能及应用性能研究。研究结果表明：Fe70Cu30本身即具有良好的热压烧结性能和很好的冷压性能;研究表明电沉积铁铜合金能够降低烧结温度,硬度没有大的变化,抗弯强度普遍有不同程度提高。根据应用试验结果,我们认为电沉积铁铜合金在某些方面具有无法替代的作用。     

昆阳裂谷带火山活动及其碱性（钠质）火山岩系特征

位于扬子板块西缘的古大陆“昆阳裂谷”是一铁铜多金属矿产成矿区带。火山岩型铁、铜矿是该裂谷带成矿的主要类型。本文从火山岩时空分布、演化及火山岩系岩石学、岩石化学和火山岩形成条件等方面阐述了裂谷带火山活动特征及人山作用与成矿的关系。     

SiO_2和B_4C的组合对铁铜基摩擦材料性能的影响

研究了摩擦组元SiO_2和B_4C的组合对铁铜基摩擦材料性能的影响,结果发现,在摩擦组元总量不变的情况下,随SiO_2的增加和B_4C的减少,摩擦材料的摩擦系数和磨损量均下降,材料的摩擦系数随制动速度的增加降低,随制动压力的增加亦降低,通过相结构分析,烧结摩擦材料中的B_4C相已被Fe_2B相取代。     

Fe-Cu 系机械球磨合金化研究

目的为了实现Fe粉和Cu粉的合金化及观察其过程变化。方法采用机械球磨的方法,利用扫描电子显微镜等仪器,对球磨过程中的组织演变过程及微观形貌进行了研究。结果通过球磨得到了十几个纳米尺寸的晶粒。结论通过球磨可以得到过饱和固溶体。     

高能球磨制备Fe-Cu纳米晶过饱和固溶体

对Fe-20at%Cu合金粉末进行了高能球磨,并利用XRD对Fe-Cu二元合金粉末在球磨过程中的物相变化进行了分析。结果表明,球磨30 h后形成了Fe(Cu)纳米晶过饱和固溶体。热力学计算分析指出,Fe-Cu二元系不具有形成过饱和固溶体的热力学驱动力。高能球磨在Fe-Cu二元互不溶体系中扩展固溶度的驱动力是动力学驱动。在随后的退火过程中,纳米晶过饱和固溶体发生分解。