Search Results (5)

Degradation of industrial machinery through wear can be mitigated with the deposition of protective coatings to reduce maintenance costs and prolong their service lifespans. Electroless nickel-based composite coatings is one possible method used to provide this protection. The addition of Tribaloy (CoMoCrSi alloy) particles has been found to produce composite coatings with high toughness. In this work, electroless Ni-P-Tribaloy composite coatings were plated on AISI 1018 steel substrates and subjected to low-stress abrasion tests following ASTM G65 standards to investigate the abrasion of the coating. The test was performed at 10 revolution increments, with a 45 N applied load, until coating failure was observed and the measured abrasion was reported as volume loss. The two Ni-P-Tribaloy coating samples lasted for 90 and 100 revolutions, exhibiting a wear rate of 0.170 mm³ per revolution, compared to 0.135 mm³ per revolution for the Ni-P coatings. The abrasive wear mechanism in the Ni-P-Tribaloy coating was found to be plowing of the matrix around the Tribaloy particles, followed by the removal of the particles once they are protruding, which subsequently contributes to the three-body wear of the coating. The particle removal was accelerated at the coating particle-matrix interface. It is concluded that the size of the Tribaloy is a major factor, and we recommend that further studies be carried out using finer particles to improve the wear resistance of the Ni-P-Tribaloy coating. Full article

Oil and gas pipelines are subject to various forms of damage and degradation during their operation. Electroless Nickel (Ni-P) coatings are widely employed as protective coatings due to their ease of application and unique properties, including high wear and corrosion resistance. However, they are not ideal for protecting pipelines due to their brittleness and low toughness. Composite coatings of higher toughness can be developed through the co-deposition of second-phase particles into the Ni-P matrix. Tribaloy (CoMoCrSi) alloy possesses excellent mechanical and tribological properties making it a potential candidate for a high-toughness composite coating. In this study, Ni-P-Tribaloy composite coating consisting of 15.7 vol.% Tribaloy was successfully deposited on low-carbon steel substrates. Both the monolithic and the composite coatings were studied to evaluate the effect of the addition of Tribaloy particles. The micro-hardness of the composite coating was measured to be 6.00 GPa, 12% greater than that of the monolithic coating. Hertzian-type indentation testing was carried out to investigate the coating’s fracture toughness and toughening mechanisms. The 15.7 vol.% Tribaloy coating exhibited remarkably less severe cracking and higher toughness. The following toughening mechanisms were observed: micro-cracking, crack bridging, crack arrest, and crack deflection. The addition of the Tribaloy particles was also estimated to quadruple the fracture toughness. Scratch testing was performed to evaluate the sliding wear resistance under a constant load and a varying number of passes. The Ni-P-Tribaloy coating exhibited more ductile behavior and higher toughness, as the dominant wear mechanism was identified as material removal, as opposed to brittle fracture in the Ni-P coating. Full article

Electroless Ni-Mo-P coatings were deposited onto ceramic tiles in order to be employed as electrodes for the electrodeposition of ZnO and Cu₂O heterojunction layers. Varying conditions, such as duration, annealing of the electroless coating and applied potential, and duration for ZnO electrodeposition were studied in order to optimize the properties of the ZnO/Cu₂O heterojunctions toward improved photoelectrical performance. The coatings were evaluated in terms of morphology, crystalline structure, and by electrochemical and photoelectrical means. The obtained results indicated that a prolonged annealing treatment at low temperature is beneficial to improve the roughness and electrical conductivity of the Ni-Mo-P coating to further enhance the electrodeposition of ZnO. The morphology analysis revealed continuous and homogeneous Ni-Mo-P coatings. The formation of cube-like Cu₂O crystals with larger grain size was induced by increasing the deposition duration of ZnO. The properties of ZnO layer are much improved when a higher cathodic potential is applied (−0.8 V) for 1 h, resulting in optimum photoelectric parameters as 1.44 mA·cm⁻² for the J_SC and 760.23 µV for the V_OC value, respectively, for the corresponding heterojunction solar cell. Full article

Ceramic substrates were metallized with a Ni-Mo-P electroless coating and further modified with a polypyrrole (PPy) coating by the electrodeposition method. The properties of the polypyrrole coating were studied with the addition of a graphene oxide (GO) nanomaterial prior to the electrodeposition and its reduction degree. Fourier Transform Infrared Spectroscopy, Field-Emission Scanning Electron Microscopy, Raman spectroscopy and cyclic voltammetry were employed to characterize the properties of the coatings. The results indicated the successful synthesis of conductive electrodes by the proposed approach. The electrodeposition of PPy and its charge storage properties are improved by chemically reduced GO. The surface capacitive contribution to the total stored charge was found to be dominant and increased 2–3 fold with the reduction of GO. The chemically reduced GO-modified PPy exhibits the highest capacitance of 660 F g⁻¹ at 2 mV s⁻¹, and shows a good cyclability of 94% after 500 charge/discharge cycles. The enclosed results indicate the use of an NiMoP electroless coating, and modification with a carbon nanomaterial and conducting polymer is a viable approach for achieving functional ceramics. Full article

Unannealed CuNiMoP electrocatalyst was found active in electrochemical oxidation of glycerol, providing over 60% conversion without optimization. Prompted by this result, the same catalyst was investigated for the thermochemical oxidation of glycerol. For the thermochemical oxidation of glycerol using the as-deposited electroless CuNiMoP catalyst, a 2³ full factorial design of experiments (two level factorial experiment design with three factors) to assess the influence of temperature (A), reaction time (B) and pressure (C). The major reaction products detected by high performance liquid chromatography (HPLC) were glyceric, hydroxypyruvic, tartronic, oxalic and formic acids. The factors found to be most significant for the production of glyceric and tartronic acids were A, B, C, AB and BC. The highest percent conversion obtained for 30-min and 60-min catalysts was 10.6% and 9.4%, respectively. The presence of lactic acid was observed only for the 60-min as-deposited electroless CuNiMoP/Al₂O₃ catalyst. The results suggest the feasibility of an inexpensive catalyst based on non-noble metals for the thermochemical oxidation of glycerol through the electroless deposition technique. Some differences exist between the thermochemical and electrochemical product selectivity of the CuNiMoP catalyst, and reasons are suggested for the observed differences. Full article