Formation Of Ni3P Research Articles

Corrosion resistance of composite NI-P coatings in various aggressive media

The paper studies corrosion resistance in highly aggressive media of composite nickel-phosphorus coatings after isothermal annealing at different temperatures accompanied by crystallization. The phase composition of chemically deposited Ni-P coating containing about 1% dispersed SiC was analyzed. Gravimetric method was used to determine the mass loss of the samples as a result of daily exposure to various acids and in a solution of nitric acid with a concentration from 5 to 65%, which is extremely aggressive for Ni-P coatings. At each heat treatment, the steel witness samples were used to determine the microhardness by the Vickers method at a load of 100 g. The dependence of the parameters of the corrosion process on the presence of a dispersed additive and the phase composition of the coating has been established. At low holding times the dispersed phase exhibits a barrier effect reducing crystalline phosphide Ni3P formation during annealing and corrosion resistance; meanwhile, prolonged holding at lower temperatures produces about 70% Ni3P, stable high hardness values and improved corrosion resistance values. Lowering the coating heat treatment temperature in an oxidizing environment reduces the intensity of phosphorus burn-off from the surface and decreases all coating properties. The concentration of nitric acid in the solution at the level of 5-15% is critical and contributes to the dissolution of all coatings, regardless of their composition.The conducted research and revealed regularities made it possible to determine the contribution of the phase composition and presence of the dispersed additive to the formation of the main service characteristics of the nickel-phosphorus coatings - microhardness and resistance to aggressive media, as well as to determine the technological modes of heat treatment that allow the formation of optimum properties of products used in the oil and gas industry.

(Digital Presentation) Crack-Free Ni-P Film for Power Devices

Demands for power devices are expanding with the electrification of automobiles. Power devices are soldered using Ni-P films prepared by an electrochemical method to withstand required high currents. However, cracks are inevitably induced in Ni-P films during high mounting temperatures. Ni-P films play an important role as a solder joint material and the P concentration is a critical factor that affects the mechanical properties of Ni-P films. Therefore, in this work, we focused on the P concentration and tried to prepare Ni-P films without cracks induced by high heat treatments. Ni-P films with different P concentration were formed on an Al substrate by an electroplating using a Watt bath and then investigated the relationship between the P concentration and the generation of cracks by X-ray diffraction and thermal expansion analyses. By the heat treatment at 300 °C or higher, Ni-P compounds mainly composed of Ni3P was formed in the Ni-P film with P concentration of 8 wt.% or more and the film shrank by 0.11%. In contrast, the 2 wt.% or less P- Ni film did not cause the formation of Ni3P and little shrinkage was observed even after the high treatment at 400 °C. The obtained results indicate that the phase transition to Ni-P compounds by the heat treatment is responsible for the mechanical disintegration, that is, the P concentration in the film is closely related to the generation of cracks. We propose the method for suppressing cracks by controlling the P concentration in the Ni film. Figure 1

Al(PO3)3 supported NiMo bimetallic catalyst for selective synthesis of fatty alcohols from lipids

An efficient Al(PO3)3-supported NiMo bimetallic catalyst for the hydrodeoxygenation of lipids to alcohols has been developed. A Ni-Mo synergistic catalytic effect is found, in which H2 is mainly activated by Ni0 and Ni3P sites, and lipids are mainly absorbed on Mo sites. Al(PO3)3 can not only inhibit the oxidation of Ni and Mo species, and but also promote the formation of Ni3P, both of which is favorable to the reaction. Furthermore, this material also displays excellent stability and reusability.

Microstructural stability and nanoindentation of an electrodeposited nanocrystalline Ni-1.5 wt. % P alloy

Microstructural stability of nanocrystalline Ni-1.5wt.%P alloy with an initial grain size of 3 nm processed by pulsed electrodeposition was studied using differential scanning calorimetry (DSC) and annealing. Microstructural characterization suggests that the observed exothermic peak during heating in DSC is related to both concurrent grain growth and Ni3P formation. Nanoindentation on samples with grain sizes from 3 to 50 nm revealed a breakdown in Hall-Petch strengthening in nano Ni-P alloy at grain sizes <= 10 nm, consistent with some previous observations. It is concluded that there is a grain boundary weakening regime for grain sizes < 10 nm, based on analysis which show that the data cannot be rationalized in terms of microstrain relaxation, variation in elastic modulus, texture evolution and duplex structure formation.

Partial dissolution of precipitated-calcium carbonate (P-CaCO3) in electroless nickel-phosphorus (Ni-P) coating and its surface characterization

Nickel-phosphorus/precipitated-calcium carbonate (Ni-P/P-CaCO3) composite coating was prepared on mild steel using alkaline electroless coating process. The partial dissolution of P-CaCO3 in the Ni-P matrix and its influence on the surface morphology, surface hardness, phase structure, crystal size, lattice parameters, surface roughness, and friction - wear behavior was studied. The weight dispersion of P-CaCO3 is varied as 1.0 g l−1, 2.0 g l−1, 3.0 g l−1 and 4.0 g l−1 in the electroless Ni-P bath by keeping the bath parameters constant. Reduction in the size of P-CaCO3 particle from 2 μm to 1 μm after the shake-flask method confirms the partial dissolution of P-CaCO3. Calcium rich Ni-P matrix along with the P-CaCO3 particle was observed in the morphology of Ni-P/P-CaCO3 composite coating, which is distinguished with the actual NiP matrix. Formation of Ni3P and Ni12P5 phases was affected after the weight dispersion of P-CaCO3 from 2.0 g l−1 to 3.0 g l−1 in the bath. Ni-P/P-CaCO3 composite coating presented a lower hardness of 394 HV0.05 compared to the 511 HV0.05 of Ni-P coating. Hardness decreases with the increase in the weight dispersion of P-CaCO3 in the bath. However, the friction-wear resistance of Ni-P/P-CaCO3 composite coatings was improved considerably after the reinforcement of P-CaCO3. Restriction in the formation of Ni3P and Ni12P5 phases had caused a high material removal for the Ni-P/P-CaCO3 (3.0 g l−1) composite coatings. Various wear features in the wear track such as grooves, craters, and de-lamination were characterized and elaborated in this study.

Thermal treatment to enhance saturation magnetization of superparamagnetic Ni nanoparticles while maintaining low coercive force

Superparamagnetic nanoparticles capped by insulators have the potential to decrease eddy current and hysteresis losses. However, the saturation magnetization (Ms) decreases significantly with decreasing the particle size. In this study, superparamagnetic Ni nanoparticles having the mean size of 11.6 ± 1.8 nm were synthesized from the reduction of Ni(II) acetylacetonate in oleylamine with the addition of trioctylphosphine, indicating the coercive force (Hc) less than 1 Oe. Thermal treatments of the Ni nanoparticles were investigated as a method to enhance the Ms. The results indicated that the M s was enhanced by an increase of the Ni mass ratio with increasing thermal treatment temperature. However, the decomposition behavior of the capping layers indicated that their alkyl chains actively decomposed at temperatures above 523 K to form Ni3P via reaction between Ni and P, resulting in particle growth with a significant increase in the Hc. Therefore, the optimal temperature was determined to be 473 K, which increased the Ni ratio without formation of Ni3P while maintaining particle sizes with superparamagnetic properties. Further, the Ms could be improved by 22% (relative to the as-synthesized Ni nanoparticles) after thermal treatment at 473 K while maintaining the Hc to be less than 1 Oe.

Interface Reaction Between Electroless Ni–Sn–P Metallization and Lead-Free Sn–3.5Ag Solder with Suppressed Ni3P Formation

The voids formed in the Ni3P layer during reaction between Sn-based solders and electroless Ni–P metallization is an important cause of rapid degradation of solder joint reliability. In this study, to suppress formation of the Ni3P phase, an electrolessly plated Ni–Sn–P alloy (6–7 wt.% P and 19–21 wt.% Sn) was developed to replace Ni–P. The interfacial microstructure of electroless Ni–Sn–P/Sn–3.5Ag solder joints was investigated after reflow and solid-state aging. For comparison, the interfacial reaction in electroless Ni–P/Sn–3.5Ag solder joints under the same reflow and aging conditions was studied. It was found that the Ni–Sn–P metallization is consumed much more slowly than the Ni–P metallization during soldering. After prolonged reaction, no Ni3P or voids are observed under SEM at the Ni–Sn–P/Sn–3.5Ag interface. Two main intermetallic compounds, Ni3Sn4 and Ni13Sn8P3, are formed during the soldering reaction. The reason for Ni3P phase suppression and the overall mechanisms of reaction at the Ni–Sn–P/Sn–3.5Ag interface are discussed.

Electromigration Study on Sn(Cu) Solder/Ni(P) Joint Interfaces

This study investigates the electromigration (EM) effect under a high current density (104 A/cm2) on the different interfacial compound phases at Sn(Cu) solder/electroless nickel immersion gold (ENIG) interfaces. The interfacial Ni3Sn4 phase at the Sn-0.7 wt.%Cu/ENIG joint interface was quickly depleted after a short period (50 h) of current stressing. The inference drawn is that the Ni atoms in the Ni3Sn4 phase at the joint interface are likely forced out under current stressing; however, the ternary (Cu,Ni)6Sn5 compound effectively reduces the EM-driven Ni flux into the Sn bump; thus, a significantly lower Ni(P) consumption was observed at the Sn-1 wt.%Cu/ENIG interface. The EM-induced Ni(P) dissolution rates in the Sn-0.2 wt.%Cu/ENIG and Sn-1 wt.%Cu/ENIG cases were calculated to be 0.028 μm/h and 0.018 μm/h, respectively. In addition, significant EM-assisted Ni3P formation was observed for the current-stressed Sn-0.2 wt.%Cu/ENIG and Sn-0.7 wt.%Cu/ENIG cases; however, for the Sn-1 wt.%Cu/ENIG case, formation of a Ni3P layer was scarcely observed. Moreover, the initial (Cu,Ni)6Sn5 that formed at the interface appeared compact with a layer-type structure, which reduced the EM-driven Ni diffusion.

The influence of Pd on growth behavior of a quaternary (Cu,Ni,Pd)6Sn5 compound in Sn–3.0Ag–0.5Cu/Au/Pd/Ni–P solder joint during a liquid state reaction

This study investigated the liquid state reaction of a Sn–3.0Ag–0.5Cu solder jointed with electroless Ni–P/immersion Au (ENIG) and electroless Ni–P/electroless Pd/immersion Au (ENEPIG) surface finishes. Treatments with various soldering temperatures (240, 250, and 260 °C) and times (60, 180, 300, and 600 s) were performed to study the microstructure evolution. Detailed interfacial images revealed that the morphology of (Cu,Ni)6Sn5 affects the formation of Ni3P and the curvature of the interface between them. In addition, the growth kinetics of (Cu,Ni)6Sn5 and (Cu,Ni,Pd)6Sn5 were studied and compared. The effect of grain coarsening during extended reflow modified the diffusion transport mechanism. However, because of the refinement of Pd on the grain structure, reduced IMC growth and a lower degree of transition from grain boundary diffusion to volume diffusion could be observed in the growth kinetics of (Cu,Ni,Pd)6Sn5. Moreover, the activation energy of IMC growth was evaluated using the Arrhenius equation. Pd may act as heterogeneous nucleation sites in the initial stage of soldering and lower the activation energy of (Cu,Ni,Pd)6Sn5, compared to (Cu,Ni)6Sn5. The lower activation energy of (Cu,Ni,Pd)6Sn5 growth ensured that no phase transformation occurred in the SAC305/ENEPIG joints, which may benefit the solder joint reliability. Finally, the detailed influence of Pd on the growth kinetics of IMC formation was investigated and discussed.

Abrasive wear resistance of electroless Ni–P coated aluminium after post treatment

Electroless nickel (EN) coatings are recognised for their hardness and wear resistance in automotive and aerospace industries. In this work, electroless Ni–P coatings were deposited on aluminium alloy substrate LM24 (Al–9 wt.% Si alloy) and the effect of post treatment on the wear resistance was studied. The post treatments included heat treatment and lapping with two different surface textures. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and micro-abrasion tester were used to analyse morphology, structure and abrasive wear resistance of the coatings. Post heat treatment significantly improved the coating density and structure, giving rise to enhanced hardness and wear resistance. Microhardness of electroless Ni–P coatings with thickness of about 15 μm increased due to the formation of Ni 3P after heat treatment.

Effects of Zn addition on the drop reliability of Sn–3.5Ag–xZn/Ni(P) solder joints

Varying amounts of Zn (1, 3, 7 wt%) were added to Sn–3.5Ag solder on the electroless Ni(P)/immersion Au metallization, and solder joint microstructures after reflow and isothermal aging (500 h at 150 °C) were investigated using scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, and x-ray diffraction, which were subsequently correlated to the microhardness and drop test results. Zinc in the solder affected the solder joint intermetallic compounds profoundly, which improved the drop reliability significantly. The effect of Zn was to nucleate Ni5Zn21and to suppress the formation of Ni3P, Ni3SnP, and Ni3Sn4, which were known to increase the propensity for brittle cracking. Drop test results showed an inverse correlation between the number of drops-to-failure (Nf) and the thickness of Ni3P layer. As the growth of the Ni3P layer was suppressed by Zn, drop reliability increased substantially.

Effect of phosphorous content on phase transformation induced stress in Sn/Ni(P) thin films

The film stress evolutions induced by the phase transformation of Sn/Ni(P) films during thermal treatment were investigated using an in situ measurement of wafer curvature by laser scanning. Apparently, tensile stress developed due to the layer-by-layer formation of Ni3Sn4 and Ni3P phases for Sn/Ni(11.7P) films, and a compressive stress evolved for Sn/Ni(3P) films, despite the same phase transformation. The molar volume mismatch and x-ray diffraction analyses before and after the reaction between Sn and Ni(P) films suggested that a compressive stress existed in the Ni3Sn4 layer while the Ni3P layer was under a tensile stress state. The apparent stress states (tensile or compressive) for overall thickness of the films formed by the layer-by-layer transformation in Sn/Ni(P) were determined by the competition between compressive stress related to Ni3Sn4 formation and tensile stress caused by Ni3P formation. The stress states were dependent upon the relative thickness of the product layers with varying P content.

Cavitation erosion behavior of electroless nickel-plating on AISI 1045 steel

Electroless nickel-plating is widely used in anti-corrosion engineering with a bonus of the capability of precipitation hardening due to Ni 3P formation after a 1 h heat treatment at 400 °C. But its application in cavitation erosion protection has been rarely discussed in the literature. In this study, electroless nickel-plating is produced on AISI 1045 steel with and without post-heat treatment and cavitation erosion test is evaluated. The test was carried out both in distilled water and 3.5 wt.% NaCl solution, respectively. The results showed that the specimen having an electroless nickel film, without post-heat treatment, underwent an easy flaking-off during both cavitation erosion tests, whereby the cumulative mass loss of the specimens was much higher than the mass loss of the blank steel substrate or the electroless nickel-plating with post-heat treatment (PHT) due to weak adhesion strength of film. Specimens, which had undergone post-heat treatment showed a dramatic reduction in cumulative mass loss in both distilled water and 3.5% NaCl solution. The damage developed on the surface of the specimen suggests that the progress of material removal via fatigue was caused by the brittle nature of the PHT nickel-plating layer. From an electrochemical point of view, the PHT specimen resembled the as-plated specimen in 3.5 wt.% NaCl solution, indicating that the cavitation resistance of the PHT specimen originated from enhanced mechanical strength due to precipitation hardening. However, when the plated nickel film is eroded, a galvanic corrosion will start between the plated film and the steel substrate damaging the steel substrate, especially in cavitation erosion systems.

Correlation between interfacial reactions and mechanical strengths of Sn(Cu)/Ni(P) solder bumps

The correlation between interfacial reactions and mechanical strengths of Sn(Cu)/Ni(P) solder bumps has been studied. Upon solid-state aging, a diffusion-controlled process was observed for the interfacial Ni-Sn compound formation of the Sn/Ni(P) reaction couple and the activation energy is calculated to be 42 KJ/mol. For the Sn0.7Cu/Ni(P), in the initial aging, a needle-shaped Ni-Sn compound layer formed on Ni(P). Then, it was gradually covered by a layer of the Cu-Sn compound in the later aging process. Hence, a mixture layer of Ni-Sn and Cu-Sn compounds formed at the interface. For the Sn3.0Cu/Ni(P), a thick Cu-Sn compound layer quickly formed on Ni(P), which retarded the Ni-Sn compound formation and resulted in a distinct Cu-Sn compound/Ni(P) interface. The shear test results show that the mixture interface of Sn0.7Cu bumps have fair shear strengths against the aging process. In contrast, the distinct Cu-Sn/Ni(P) interface of Sn3.0Cu solder bumps is relatively weak and exhibits poor resistance against the aging process. Upon the reflowing process, the gap formation at the Ni(P)/Cu interface caused a fast degradation in the interfacial strength for Sn solder bumps. For Sn0.7Cu and Sn3.0Cu solder bumps, Ni3P formation was greatly retarded by the self-formed Cu-Sn compound layer. Therefore, Sn(Cu) solder bumps show better shear strengths over the Sn solder bump.

Thermal stability and microstructure characterization of sputtered Ni–P and Ni–P–Cr coatings

Ni–P and Ni–P–Cr alloy coatings were deposited onto silicon substrates by the RF magnetron sputtering technique with dual targets of electroless nickel–phosphorus alloy and chromium. To evaluate the effect of doping with a third element on the enhancement of thermal stability in Ni–P coatings, differential scanning calorimetry (DSC) was used to identify the onset temperature of phase transformation. The crystallization behavior at different stages of phase transition in the DSC plot was further evidenced by X-ray diffraction (XRD). Microstructural evolution of the Ni–P based coating in the as-deposited and heat-treated states were investigated by transmission electron microscopy (TEM). The broad peak in the DSC plot of both Ni–P and Ni–P–Cr deposits is attributed to the grain coarsening of nickel on the basis of XRD and TEM analyses. The addition of Cr atoms into Ni–P based coating not only suppresses the formation of Ni 3P but also reduces the grain size of precipitates.

Interface microstructures between Ni-P alloy plating and Sn–Ag–(Cu) lead-free solders

The interface microstructures of Sn-Ag and Sn-Ag-Cu solders with Au/Ni-6P plating were studied primarily using transmission electron microscopy. During soldering at 230°C, Au dissolved into molten solder, and double reaction layers of Ni3Sn4/η–Ni3SnP formed between Sn-3.5Ag solder and Ni-6P layer. P content increases in the surface region of the Ni-6P layer due to the depletion of Ni diffused into molten solder, resulting in the formation of Ni3P+Ni layer. For Sn-3.5Ag-0.7Cu solder, an η-(Ni,Cu)3Sn2 single layer, containing Cu of about 50 at.%, formed as a reaction layer.

Effect of internal stress on elemental diffusion and crystallization of electroless Ni–Cu–P deposit on Al

The type and magnitude of stress in electroless Ni–Cu–P deposits on Al were manipulated by controlling the concentration of saccharin in the plating solution. Tensile, zero, and compressive stress of the electroless Ni–Cu–P deposits was obtained with 0, 8, and 10 g/l saccharin for studying the effect of stress on the diffusion and crystallization behavior of the deposit. The effect of stress on the diffusion behavior of Cu, Ni, and Al elements during annealing was investigated. Interdiffusion between Al and Ni in an amorphous Ni–Cu–P/crystal Al diffusion couple is abated by the effects of amorphous structure, atomic affinity, and backstress. Therefore, the effect of stress on diffusion is manifested by Cu elemental diffusion. The tensile stress promotes the formation of Ni3P and the diffusion of Cu into the substrate.

Microstructure and catalytic activity towards the hydrogen evolution reaction of electrodeposited NiP x alloys

Electrodeposited NiP x alloys have been studied using electrochemical techniques, transmission electron microscopy and electron diffraction. The results show that crystals in the nanometer range are ‘floating’ in an amorphous phase. The crystal size is correlated with the catalytic activity of hydrogen evolution in an alkaline solution. It was found that the activity increased when the crystal size decreased. Electron diffraction patterns of the crystals showed that when few crystals were observed, they were found to be pure Ni. Ni 3P was found only when considerable amount of crystals had been formed. With the formation of Ni 3P the activity was reduced. It is proposed that the increased catalytic activity is caused by an increased amount of amorphous phase surrounding the Ni crystals. This phase is able to absorb large amounts of hydrogen, thereby changing the electronic structure of the electrode material.

Three-dimensional atomic scale analysis of nanostructured materials

The 3-dimensional atom probe (3DAP) has been used to provide atomic-scale microcharacterisation of a number of nanostructured materials. Grain boundary segregation has been investigated in electrodeposited nanocrystalline nickel and Ni-P. In the nanocrystalline nickel, there was no observable grain boundary segregation in the as-deposited condition. After annealing, carbon and sulphur contamination was found at the boundary of an abnormally-grown grain. In the as-deposited Ni-P alloy, only limited grain boundary segregation of P is seen, but annealing produces significant segregation and the formation of Ni 3P precipitates at grain boundaries. The phase chemistry in a melt-spun amorphous Fe-Si-Cu-Nb-B-Al (FINEMET-type) alloy has also been studied, and the hetereogeneous nucleation of Fe-Si nanocrystals at Cu precipitates shown conclusively. It is found that at early stages of crystallisation, there is only limited partitioning of the Si between the nanocrystals and the amorphous matrix. Atom probe studies of thin layered films have historically been limited by specimen preparation problems, but recent advances have now yielded data on metallic multilayer films. This has allowed atomic-scale measurements of interface chemistry in these films for the first time.

Atomic Scale Characterisation of Electrodeposited Nanocrystalline Ni-P Alloys

ABSTRACTNanocrystalline Ni-P alloys produced by electrodeposition have been characterised by three-dimensional atom probe (3DAP) analysis. In the as-deposited materials, there are indications of some variation in P concentration between grains and segregation to grain boundaries. After heat treatment however, strong grain boundary segregation and the formation of Ni3P precipitates have been observed.