Temperature,current density and cobalt concentration effects on electrodeposited anticorrosive cobalt-tungsten alloys using factorial experiment design and ANOVA techniques

ABSTRACT

Corrosion processes can compromise the durability of metallic materials. One way to minimise the effects of corrosion is to coat them with corrosion-resistant alloys. In this study, Co–W alloys were produced by electrodeposition and their anticorrosive performance was evaluated at different levels of current density, Co bath concentration and bath temperature, using factorial experiment design and ANOVA techniques. This evaluation consisted of measuring corrosion current and using electrochemical impedance spectroscopy. Adherent and corrosion resistant alloys were obtained at the lowest temperature of experimental design (25°C) and current density (10?mA?cm^?2) values. From the corrosion tests, X-ray Diffraction and Scanning Electron Microscopy analysis it was possible to conclude that the increase in the tungsten percentage in the composition of the alloy generated an increase in corrosion resistance. Although the alloys’ chemical composition has influence on the corrosion resistance, their physical aspect, such as the presence of cracks, are more significant for the resistance to corrosion.     

高速钢微径立铣刀的Ni-Mo-P化学镀工艺

基于化学镀Ni-Mo-P具有高硬度、表面光洁、可在复杂型面上获得均匀镀层等优点,将其应用于高速钢微径立铣刀上,并通过铣削试验对镀层性能进行分析。结果表明:Ni-Mo-P三元合金镀层对于提高高速钢微径立铣刀的表面硬度、增强局部刚性具有一定效果;镀层结合力是影响Ni-Mo-P化学镀在高速钢微径刀具上推广应用的关键制约因素。     

Modeling the pathways and attenuation of nutrients from domestic wastewater treatment systems at a catchment scale

Domestic Wastewater Treatment Systems (DWTS) are often cited as significant sources of pollution in rural catchments. A mass balance based model has been developed to determine annual nutrient loading from individual DWTS into rivers in Ireland. The transport and attenuation of nitrogen and phosphorus in DWTS effluent to groundwater and surface water has been formulated using the results from field research in Ireland, as well as being informed by other international studies. Conceptually the model splits the transport of nutrients to the river into three pathways: direct to surface water (for areas of inadequate percolation), a near surface (subsoil) pathway, and a groundwater pathway. The model quantifies the net nutrient contribution for each DWTS and has been incorporated into a broader source load apportionment catchment model which includes agricultural inputs, thereby enabling the relative risk of nutrient pollution from DWTS in a catchment to be defined.     

用于纺织品表面永久改性的工业真空等离子体技术

通过等离子体处理,合成材料(如涂覆聚氨酯的聚酯或聚酰胺)表面的黏附性得以显著提高。研究还表明:通过聚合物和非聚合物形成的气体混合物引入极性基团,可显著改善材料的亲水耐久性;且可聚合性气体,如CH_4,C_2H_2,C_2H_4及其混合物,或诸如丙烯酸、硅氧烷等一些液体单体,对织物表面永久性亲水、防油和防污改性方面发挥着重要的作用。     

Measurement on the structural,morphological, electrical and optical properties of PANI-CSA nanofilms

Camphorsulfonic acid doped polyaniline (PANI-CSA) prepared by chemical oxidative polymerization is spin coated on glass plates with four different PANI:CSA weight ratios (1:1, 1:2, 1:4 and 1:8) and measurements on the structural and optical properties are done. Thickness of the films measured <100 nm are termed as nanofilms. Fourier transform infrared spectroscopy indicated the presence of dopant and an increase in degree of polymerization with increase in dopant ratio. X-ray diffraction studies revealed the change of amorphous nature of the film to crystalline nature with increase in CSA dopant ratio. Scanning electron microscopy showed the change of very smooth morphology of the film to rough root-like morphology with increase in CSA dopant ratio. Hall-effect analysis showed that the increase in CSA weight ratio appreciably increases the conductivity of PANI-CSA films due to increase in carrier concentration and it also represents the semiconductivity (P-type) nature in all the films. UV–visible absorption studies reveal the broadening of absorption spectrum in visible region with maximum CSA dopant ratio (1:8). Photoluminescence spectra of PANI-CSA films excited using 300 nm, revealed that the change in intensity and position of emission peaks are due to transition of semiconducting nature of the film to conducting nature with an increase in CSA dopant ratio from 1:1 to 1:8.     

镀锌机组清洗槽刷辊枢轴劣化倾向分析与对策

针对镀锌清洗槽工艺特点,结合生产实际,重点分析了刷辊枢轴装置产生劣化倾向的原因,提出了相应措施并加以实施,提升了清洗槽设备整体工作性能,对提高产品质量产生积极影响。     

Effect of YSZ-incorporated glass-based composite coating on oxidation behavior of K438G superalloy at 1000 °C

A glass-based composite coating incorporating YSZ particles was prepared by sintering on K438G superalloy substrates. The YSZ additions increased the cyclic oxidation resistance at 1000 °C, while the formation of zircon resulting from interfacial reactions between YSZ and the glass matrix worked reversely. Besides, the YSZ inclusions changed the crystallization behavior of the glass matrix, and only anorthite precipitated during cyclic oxidation. Due to the synergy of sand-blasting and sealing effect of the glass-based coating, the oxidation behavior of K438G was changed and a layer of alumina instead of chromia formed at the substrate/coating interface. Furthermore, a gahnite layer formed at the alumina/gahnite interface because of interfacial reactions between alumina and the glass matrix, leading to the formation of a bi-layered thermally grown oxide. Thus, the alumina layer was protected from the attack of the active glass matrix. Accordingly, the coated K438G superalloy exhibited satisfactory oxidation resistance at 1000 °C.     

Effect of ecofriendly sealing coat against corrosion protection of steel rebars in concrete

Phosphating is one of the most important chemical conversion treatments for steel, mainly to improve corrosion resistance and paint adhesion and as an absorbing layer for waxes, oils, lacquers, etc. However, phosphate coating are crystalline and porous and need a sealing treatment after phosphating. Chromate sealing is a well known practice, and due to its toxicity, development of an ecofriendly sealing treatment is very essential. This paper focuses on the effect of zinc phosphate chemical conversion coating with the addition of nano-SiO₂ to protect the mild steel rebars against corrosion in chloride contaminated concrete. The coated surfaces were characterised by scanning electron microscopy and X-ray diffraction. Corrosion resistances of coated and uncoated rebars were evaluated by anodic polarisation, linear polarisation resistance, Tafel and alternating current impedance spectroscopy and cyclic polarisation technique. The results indicated that the coated rebars have considerably reduced the corrosion rate even in the presence of 3% chloride environments.     

The effects of multifunctional coating on Li-rich cathode material with hollow spherical structure for Li ion battery

Structural stability and high ionic and electronic conductivity are crucial for the performance of Li-ion batteries. To improve the electrochemical performance of Li-rich Mn-based cathode material, we have adopted a combination of bulk doping and surface coating rather than a single modification, thereby enhancing structural stability and conductivity. This combination is achieved tactfully by one-step method using surface coating on hollow material. After coating and treatment at high temperature, elements from coating layer substitute transition metal elements and distribute gradiently throughout the entire shell of cathode material, showing collective advantages of element doping and surface coating. The modified samples show enhanced rate capability and cycling stability. We discuss the relationship between battery performance and structural improvement.     

Managing clay minerals in froth flotation—A critical review

Clay minerals are widely present in various ore deposits as gangue minerals. The processing of high-clay-content ores is becoming a significant challenge for the mining industry owing to the poor flotation performance caused by the presence of clay minerals. Different types of clay minerals are typically present in ore bodies, and they cause several detrimental effects to flotation that require different treatments. In this article, a comprehensive review of the studies on understanding and mitigating the negative effects of clay minerals in flotation is presented. It starts with a review of the classification and structures of clay minerals commonly occurring in ore deposits and their properties that determine the behavior of clay minerals in flotation. It is followed by a critical review of two main negative effects of clay minerals on flotation, the recent research findings mainly from The University of Queensland group. The first negative effect is the coating of clay minerals on the surface of valuable minerals that decreases the floatability of valuable minerals. The second negative effect is the formation of network structures in the slurry. Depending on the type and strength of the network structure, it can cause either high pulp viscosity or increased gangue entrainment, which reduces the flotation recovery and flotation product grade, respectively. In this section, the mechanisms and key factors behind each negative effect are presented and critically discussed. Then, the approaches and techniques developed to mitigate the different negative effects of clay minerals are reviewed. To conclude, future directions for a more complete understanding of mechanisms and problem solving are recommended.