Influence Of Ni Addition Research Articles

High Temperature Corrosion Behavior of Si-Containing Alloys in the Liquid Phase of Na<sub>2</sub>SO<sub>4</sub> 25.7 Mass% NaCl

The high temperature corrosion behavior of Si-containing alloys consisting of Cr-Si-Ni and CoNiCrAlY-Si alloys fabricated by spark plasma sintering technique was investigated in the liquid phase of Na2SO4 + 25.7 mass% NaCl at temperatures ranging from 923-1273 K. The purpose of this study is to develop excellent corrosion resistant alloys for coating applications. Our experimental results show the CrSi2 alloy with 10 mass% Ni content and the CoNiCrAlY alloy with 30 mass% Si content are the most promising materials for applications in this atmosphere. This is due to the formation of a protective SiO2 and Al2O3/SiO2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO2 plays a significant role in hindering the inward diffusion of chlorine and sulfur to the alloys substrate. Particularly, the corrosion mechanism of Cr-Si-Ni alloys and the influence of Ni addition on the corrosion resistance of CrSi2 alloy are discussed in the present paper.

Influence of Ni addition on the process of phase formation in MgB2 bulk

Nickel is an important sheath material for the fabrication of MgB2 wires. However, the effects of Ni doping on the phase formation and superconducting properties of MgB2 remain controversial. In this work, Ni powder is selected for doping in MgB2 bulk in order to examine the corresponding changes. Combining with the DSC analysis and in-situ XRD results, we find indications that the Ni powder reacted with Mg and B, forming MgNi2.5B2 at 600°C. The ternary compound began to decompose at a temperature above 800°C. The reactive phase, MgNi2.5B2, acted as an obstacle to the supercurrent flow, creating weak links among the MgB2 grain boundaries. However, it is found that the added Ni formed a eutectic liquid phase with Mg at 506°C. The liquid phase helps the formation of MgB2 at low temperature, which not only increases the density of the sample, but also improves the grain connectivity. Consequently, the presence of Ni in the MgB2 sample is not necessarily a disadvantage; it depends on the desired application.

Influence of Ni addition on structure and magnetic properties of FeCo-based Finemet-type alloys

Structure and magnetic properties of melt-spun Nix(Fe0.5Co0.5)73.5−xSi13.5B9Nb3Cu alloys (x = 5,10,15,20,25,30) annealed at different temperatures were investigated. Microstructure has been analyzed from XRD patterns. Magnetic properties were mainly studied by the evolution of initial permeability from room temperature to 740 °C. All the 500 °C–annealed samples gave rise to an ultrafine structure composed of a residual amorphous matrix andα-FeCoNi(Si) crystals (tens of nanometers in size). It was found that Ni content had a significant impact on the Curie temperature of amorphous phaseTcam and initial permeabilityμi. There was a general reduced tendency ofTcam with Ni content increasing. For higher Ni content alloys (x≥25) annealed at 500 °C, theμi can be enhanced to the order of 104, which is much higher than that of Ni-free FeCo-based Finemet-type alloys. The reason for the enhancement inμi was systematically analyzed in terms of the effective anisotropy model.

Solidification Mechanisms in the Sn-Cu-Ni Lead-Free Solder System

Pb-free solders based on near-eutectic Sn-0.7Cu-xNi alloys provide excellent solderability during wave soldering with cost advantages compared to Ag-containing alternatives. However, there is only limited knowledge of the solidification mechanisms in this alloy system and, furthermore, the ternary Sn-Cu-Ni phase diagram is not yet fully established. In this study, unidirectional solidification has been conducted in a Bridgman furnace using both binary alloys from the Sn-Cu6Sn5 system and ternary Sn-rich Sn-Cu-Ni alloys. The influence of Ni additions on the solidification mechanisms is assessed by comparing the microstructures of the ternary and binary alloys. The results are used to discuss the contrasting Sn-Cu-Ni phase diagrams reported in the literature. The results demonstrate the complex phase relations in the Sn-Cu alloy system, and the important role of trace amounts of various solute elements.

The effect of carbide precipitate morphology on fracture toughness in low‐tempered steels containing Ni

Nickel is known to increase the resistance to cleavage fracture of iron and decrease a ductile-to-brittle transition temperature. The medium-carbon, low-alloy martensitic steels attain the best combination of properties in low-tempered condition, with tempered martensite, retained austenite and transition carbides in the microstructure. This paper is focused on the influence of Ni addition (from 0.35 to 4.00%) on the microstructure and fracture toughness of structural steels after tempering. In this research, four model alloys of different concentration of Ni and constant concentration of carbon and other elements were used. All samples were in as-quenched and tempered conditions. Quenching was performed in oil at room temperature. After quenching, samples were tempered at 200 degrees C for 2 h. The microstructure of the investigated steels was analyzed using JEM200CX transmission electron microscope. An increase of nickel content in the investigated structural steels causes a decrease of epsilon carbide concentration in their microstructure after tempering. In these steels, cementite precipitates independently in the boundaries of martensite needles and in the twin boundaries in the areas where the Fe(2.4)C carbide has been dissolved. These results will be used to design new technologies of tempering of structural steels with nickel addition.

The influence of Ni additions on the relative stability of η and η′ Cu6Sn5

We investigate how 5 at. % Ni influences the relative stability of η and η′ Cu6Sn5. Synchrotron x-ray diffraction shows that, while Cu6Sn5 exists as η′ at 25 and 150 °C and transforms to η on heating to 200 °C, Cu5.5Ni0.5Sn5 is best fit to η throughout 25–200 °C. Our first principles calculations predict that η′ is stable at T=0 K in both Cu6Sn5 and Cu5.5Ni0.5Sn5, but that the energy difference is substantially reduced from 1.21 to 0.90 eV per 22 atom cell by the Ni addition. This effect is attributed to Ni developing distinct bonding to both Cu and Sn in the η phase.

Adição de níquel na solução nutritiva para o cultivo de mudas de umbuzeiro

Com o objetivo de avaliar a influência da adição de Ni na solução nutritiva de Hoagland & Arnon sobre o crescimento e a nutrição mineral de mudas de umbuzeiro, realizou-se este trabalho. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições e seis doses de Ni (0; 0,0005; 0,05; 0,1; 0,5 e 1,0 mmol L-1). Observou-se que o Ni, em pequenas concentrações, estimula o crescimento de mudas de umbuzeiro em solução nutritiva; para o cultivo destas em solução nutritiva de Hoagland & Arnon, recomenda-se a adição de 0,03 mmol L-1 de Ni.

STEM-X-EDS analysis of morphotropic PZT ceramics: Analysis of Zr/Ti + Zr values fluctuation depending on microstructure and synthesis route of powders

A TEM-EDS analysis technique is applied to estimate dopant incorporation and Zr/Zr + Ti fluctuation in morphotropic PZT ceramics starting from powders synthesized by two routes. A solid-state synthesis route leads to less reactive powders requiring severe conditions to reach full densification. The hydrothermal route leads to more reactive powders that can be fully densified at lower temperature. In addition, the influence of Ni addition was analyzed. Zr/Zr + Ti fluctuations were estimated by the standard deviation of concentrations carried out by chemical analyses. It was shown that there is no significant partitioning of Zr and Ti inside a grain or in the ceramic. Each PZT material appears to be homogenous with a constant value of standard deviation of Zr/Zr + Ti ratios. The obtained values depend mainly on the presence or not of Ni addition whatever the nature of the chosen synthesis route. Standard deviation values of Zr/Zr + Ti ratios appear to be in accordance with literature values estimated by high temperature X-ray diffraction broadening. Results are also discussed relatively to some piezoelectric properties and more particularly to the quality mechanical factor.

Influence of Ni additions on the low-temperature magnetic properties of a Cu–1% Mn alloy

dc susceptibility and magnetization measurements were made on three alloys with the nominal compositions Cu–1% Mn, Cu–15% Ni, and Cu–1% Mn–15% Ni. dc susceptibility [χdc=C/(T+θW)] measurements were made with a Curie-type balance from room temperature down to 77.2 K. Magnetization measurements consisted of M-H loops at 4.2 and 1.37 K, and initial magnetization runs from room temperature down to 1.37 K. The results were analyzed in terms of an addition of Ni to Cu-Mn. High-temperature χdc data were used to find θW, C, and μeff (from C and the concentration), and it is found that these properties are influenced only to a minor extent by the Ni addition. At low temperatures, however, a suppression of the freezing temperature and an enhancement in the superparamagnetic signal are noticed for Cu-Mn-Ni as compared to Cu-Mn. Finally, hysteretic loss and magnetization for the ternary at 4.2 K were compared to that of the Cu-Ni and Cu-Mn alloys in order to determine its suitability for use as matrix material in multifilamentary superconductive wire.

The effect of Ni addition on the corrosion behaviour of sintered stainless steel in H2SO4

The influence of Ni addition on the corrosion behaviour of hot pressed sintered stainless steel of type 316 in H2SO4 solution was investigated. It was found that Ni additions enhance the passivation processes of the hot-pressed stainless steel. The corrosion resistance was substantially improved by the Ni addition after 48 h of sintering, and the weight loss was negligible as compared to corrosion up to total loss identified in the hot-pressed and sintered 316 stainless steel. It is suggested that threshold microstructure conditions are necessary for the passivation processes of sintered stainless steel, depending on the alloying element.

On the Sintering of the Fe-Ni-C Ternary Mixed Powder Compacts

Using mixed powder compacts of Fe-Ni-1.0 wt%C system with different Ni contents and Fe-4.0wt%Ni-C system with different graphite contents, the influence of Ni addition on the carburization and the dimensional changes were investigated by means of the differential dilatometric method and carbon analysis.The results obtained are summarised as follows:(1) Carbon content combined during heating process up to 900°C, which is about 0.1 wt% in a Fe-1.0 wt%C binary compact, increases with increasing Ni content in Fe-Ni-1.0 wt%C ternary compacts.(2) In the case of the ternary compacts which content carbonyl Ni powder, the sintering rate is remarkably promoted. Also the sintering promotive effect is observed in Fe-carbonyl Ni-1.0 wt%C compacts. These results suggest that the shrinkage due to the sintering of fine powders plays an important role in the promotion of sintering.(3) The combined carbon concentration of the Fe-1.0 wt%C binary sintered compact is nearly the same as that of eutectoid composition. However in Fe-Ni-1.0 wt%C ternary sintered compacts, some hypereutectoid regions are observed, because the carbon concentration lowers with increasing Ni content along the Fe-Ni-C ternary eutectoid line. Therefore the retained shrinkage increase remarkably by the contraction due to the precipitation of primary cementite in the Ni content more than 6 wt%Ni.