1,725,620 research outputs found
Preparation and temperature cycling reliability of electroless Ni(P) under bump metallization
Full text linkThe reliability of electroless Ni(P) under-bump metallization (UBM) was evaluated via temperature cycling and solder bump shear strength tests. Commercial diodes and dummy dies fabricated in-house were used as substrates for the electroless Ni(P) UBM deposition. Solder bumps were formed after reflowing eutectic 63Sn37Pb solder foils over the Ni(P) UBM. The solder bump shear strength was measured before and after different temperature cycling. The results from this study showed that the UBM thickness and dimension had important effects on the solder bump shear strength and reliability. Both the larger UBM dimension and larger UBM thickness tended to induce higher stress in the UBM, which resulted in the lower solder bump shear strength and lower temperature cycling reliability. A better UBM structure solution for high current electronic packaging application is indicated in this pape
Development and Characterization of Electroless Ni-P Composite Coatings With Tribaloy Additions
No full textElectroless Nickel (Ni-P) coatings are widely employed as protective coatings due to their ease of application and unique properties. However, they are limited by their brittleness. Thus, Tribaloy (CoMoCrSi) alloy is used in this study to develop a novel Ni-P composite coating with enhanced hardness and toughness. The objective of this research is to develop and characterize the Ni-P-Tribaloy composite coating, and to evaluate the effect of the addition of Tribaloy on the wear performance. Ni-P-Tribaloy coatings were successfully deposited on low carbon steel substrates. Following coating characterization, the 15.7 vol.% Tribaloy composite coating was subjected to Hertzian-type indentation, multiple-pass scratch, and low-stress abrasion tests to examine the coating’s wear behaviour under different conditions. The addition of Tribaloy was found to improve the hardness, fracture toughness, and ductility of the Ni-P coating. However, the Ni-P-Tribaloy coating exhibited high wear rates mainly due to the large Tribaloy particle size used
ELECTROLESS Ni-P-Ti BASED NANOCOMPOSITE COATINGS
No full textInfrastructures in various industries, such as oil and gas, chemical, automotive etc., are subjected to aggressive erosive and corrosive environments. A potential candidate for the protection of such infrastructures is electroless Ni-P coating owing to its high hardness and good corrosion resistance. Nevertheless, Ni-P has low toughness, which tends to readily crack and fracture under load. To toughen Ni-P coating, superelastic NiTi particles are an attractive addition. The high price of the NiTi particles, however, restricts their application. Ti particles have much lower price (5-10 times lower) than NiTi particles, which can be employed as an alternative to the NiTi particles. Therefore, to reduce cost, Ti particles were utilized as an addition in the present study. Ni-P-NiTi composite coatings with different Ti concentrations were successfully prepared on low carbon steel substrates by co-plating Ni-P and Ti nanoparticles followed by annealing of Ni-P-Ti coatings. To systematically investigate the effects of the formation of superelastic NiTi phase after annealing on the mechanical, wear, and corrosion properties of the composite coatings, a series of tests were conducted such as scratch, bend, tensile, nanoindentation, single particle erosion, corrosion, and erosion-corrosion tests. The formation of NiTi phase after annealing was substantiated by slow scan XRD, point and line scan EDS. The superelastic effect of NiTi particles was also verified by nanoindentation tests. Compared to Ni-P-Ti coatings annealed at 700°C and 800°C for 5 hours, Ni-P-Ti coatings annealed at 650°C for 2 hours exhibited higher Vickers hardness, scratch toughness, scratch resistance due to the formation of high amount of superelastic NiTi phase. Different toughening mechanisms such as crack deflection, crack bridging, transformation toughening induced by superelastic NiTi particles were observed and identified in the aforementioned tests. In conclusion, the formation of superelastic NiTi phase not only improved the toughness, scratch, indentation, erosion resistance but also considerably enhanced the corrosion and erosion-corrosion resistance of Ni-P coating. As a result, the annealed Ni-P-Ti coatings (i.e., Ni-P-NiTi coatings) may be employed to protect low carbon steel components or in applications where the high cracking resistance, high wear, or impact resistance, and/or high corrosion resistance are required
Wear and Erosion-Corrosion Behaviour of Electroless Ni-P Composite Coatings with NiTi Nanoparticle Additions
No full textElectroless Ni-P coatings have high hardness and corrosion resistance but low toughness. The addition of super-elastic NiTi nanoparticles have been previously developed and shown to improve the coating’s ductility. However, the coating’s wear and erosion-corrosion resistance needed to be assessed. Different thicknesses of Ni-P and Ni-P-NiTi coatings were developed on API X100 and AISI 1018 substrates and characterized using SEM, EDS, XRD, and micro-hardness. Their sliding wear resistance was tested by multiple pass wear tests. Slurry pot erosion-corrosion tests were conducted to assess their performance to potentially protect a pipeline under similar conditions. Using both the material loss rates and observable wear behaviour, the effect of coating thickness and the presence of particles was evaluated. It was found that the thickness of the coating greatly influences its durability, and its effectiveness differs depending on the wear process. The addition of NiTi nanoparticles demonstrated toughening mechanisms that resulted in less cracking
Electroless plating of Ni-P/PTFE composites for anti-sticking applications
No full textLAUREA MAGISTRALELa deposizione electroless è una tecnica di deposizione per metalli che non richiede elettricità e che consente l'applicazione di rivestimenti uniformi e conformi su substrati conduttivi e non conduttivi. In particolare, il la deposizione electroless di nichel ha trovato ampie applicazioni in molti settori industriali. La ricerca di proprietà migliorate ha portato a molte nuove varianti di rivestimenti in nickel electroless quali Ni-P, Ni-P/SiC, Ni-P/PTFE, Ni-P/TiO2, Ni-Cu-P, Ni-P-W. La presente review discute i rivestimenti compositi di Ni-P elettrolitici che incorporano particelle di PTFE. Il Ni-P/PTFE come materiale composito è utilizzato per via delle sue proprietà antigrippanti, del basso coefficiente di attrito, della sua uniformità, dell’elevata aderenza e delle buone proprietà di resistenza alla corrosione. Questa review studia l'effetto dell'aggiunta di PTFE in un bagno electroless, l'incorporazione di PTFE e i tipi di tensioattivi utilizzati per la corretta dispersione del PTFE. Nella parte finale, viene effettuata una sperimentazione preliminare sulla codeposizione di Ni-P con PTFE. I rivestimenti compositi ottenuti sono caratterizzati dal punto di vista morfologico e funzionale.Electroless plating is a metal deposition technique that does not require electricity and that allows the application uniform and conformal coatings on both conductive and non-conductive substrates. In particular, electroless nickel deposition has found wide applications in many industrial fields. The pursuit of improved properties has led to many newer variants of electroless nickel coatings like Ni-P, Ni-P/SiC, Ni-P/PTFE, Ni-P/TiO2, Ni-Cu-P, Ni-P-W. This review discusses the electroless Ni-P composite coatings incorporating PTFE particles. Ni-P/PTFE as a composite material is used because of its non-galling behavior, low coefficient of friction, uniformity, high adherence, and good corrosion resistance properties. This review studies the effect of PTFE addition in an electroless bath, the incorporation of PTFE, and the types of surfactants used for proper dispersion of PTFE. In the final part, some preliminary experimentation on Ni-P co-deposition with PTFE is carried out. Obtained composite coatings are characterized by the morphological and functional point of view
Síntese e sinterização de esferas ocas nanoestruturadas de Ni e Ni-P
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2013.Este trabalho apresenta uma proposta de formação de materiais metálicos de baixa densidade através da sinterização de particulados, com perspectiva de aplicação em produtos de engenharia. Estes materiais na forma de esferas ocas nanoestruturadas de níquel são sintetizados por duas rotas distintas; a rota R1 utiliza vesículas de dodecil sulfato de sódio (SDS) como máscaras de sacrifício e hipofosfito de sódio como agente redutor, para formar esferas ocas e lisas de Ni-P com diâmetro médio de 1,4 µm; já a rota R2 utiliza a hidrazina como agente redutor para depositar níquel metálico puro e nanoestruturado sobre máscaras de sacrifício de polietileno glicol (PEG) para formar esferas ocas com diâmetro médio de 0,55 µm. Um estudo preliminar da sinterização destes dois materiais através da dilatometria é comparado com o de uma amostra de níquel comercial com granulometria de 6 µm. A caracterização dos materiais particulados produzidos é feita por DRX, MEV, MEVEC e CDV; enquanto o estudo do processo da sua sinterização é realizado através da dilatometria, sendo os produtos sinterizados analisados por MO, MEV, EED e medidas de densidade.Abstract : This work presents a proposal of formation of low density metalic materials through sintering of powders, with expectation of application on engineering products. These materials in the form of nanostructured hollow spheres of nickel are synthesized by two distinct routes; route R1 uses sodium dodecyl sulfate (SDS) vesicles as sacrificial templates and sodium hypophosphite as reducing agent, to form smooth hollow spheres of Ni-P alloy and mean diameter of 1,4 µm; route R2 uses hydrazine as reducing agent to deposit pure metallic nickel nanostructured over sacrificial templates of polyethilene glycol (PEG) to form hollow spheres with mean diameter of 0,55 µm. A preliminary study of the sintering of these two materials through dilatometry is compared with a sample of commercial nickel with 6 µm average size. The characterization of the produced particulate materials is made with XRD, SEM, SEM-FEG and DSC; while the study of the sintering process is conducted through dilatometry, being the sintered products analyzed by OM, SEM, EDS and density measurements
Crystallization behaviors and microhardness of sputtered Ni-P, Ni-P-Cr and Ni-P-W deposits on tool steel
Full text link[[abstract]]The Ni-P-based coatings, including binary Ni-P, ternary Ni-P-Cr and Ni-P-W, were fabricated by the RF magnetron sputtering technique with dual target of electroless Ni-P alloy and a third metal element. To evaluate the influence of the doping element in Ni-P deposit, differential scanning calorimeter (DSC) analysis was employed to characterize the temperature of phase transformation. The phase transition during thermal evolution under heat-treatment was analyzed by X-ray diffractometry (XRD). Crystallization behavior in binary and ternary Ni-P-based coatings was quite distinct due to the addition of Cr and W. Microhardness tests indicated that the sputtered Ni-P-Cr and Ni-P-W coatings exhibited superior hardness and excellent thermal stability than the Ni-P coating. In addition, chromium exhibited compatible thermal characteristics with the tungsten for the ternary Ni-P-based system. The strengthening mechanism in the sputtered Ni-P-Cr and Ni-P-W deposits is also discussed.[[fileno]]2020323010087[[department]]材料科學工程學
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Advanced Performance of Annealed Ni-P/(Etched Si) Negative Electrodes for Lithium-Ion Batteries
Full text linkThe electrochemical performance of variously treated Ni-P-coated Si (Ni-P/Si) negative electrodes for lithium-ion batteries was investigated. X-ray diffraction analysis revealed the formation of nickel silicide (NiSi and NiSi2) after annealing, which improved the adhesion between the Ni-P coating layer and Si particles. Spotty Ni-P particles did not aggregate on an etched Si surface due to an anchor effect, even after annealing, whereas the particles aggregated on an untreated Si surface. An annealed Ni-P/(etched Si) negative electrode maintained a discharge capacity of 2000 mA h g-1 even at the 100th cycle in an organic electrolyte, which can be attributed to Ni-P particles remaining on the surface of the annealed Ni-P/(etched Si) electrode even after the charge-discharge test. The annealed Ni-P/(etched Si) electrode also exhibited superior cycle performance with a reversible capacity of 1000 mA h g-1 over 750 and 1100 cycles in an organic electrolyte containing film-forming additive and an ionic liquid electrolyte, respectively. Consequently, the annealed Ni-P/(etched Si) electrode achieved both high reversible capacity and long cycle life
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