Varying Ni Content Research Articles

The use of liposomes to differentiate between the effects of nickel accumulation and altered food quality in Daphnia magna exposed to dietary nickel

A potential drawback of traditional dietary metal toxicity studies is that it is difficult to distinguish between the direct toxicity of the metal and indirect effects caused by altered concentrations of essential nutrients in the metal-contaminated diet. In previous studies it has become clear that this can hamper the study of the real impact of dietary metal exposure and also complicates the analysis of the mechanisms of dietary metal toxicity in filter-feeding freshwater invertebrates like Daphnia magna. This problem has been partly circumvented by the production of liposomes, since these vectors are invulnerable to metal-induced food quality shifts and as such can be applied to study the mechanisms of dietary metal toxicity without the confounding effect of nutritional quality shifts. The aim of current study was to evaluate if there is relevance for dietary Ni toxicity under natural exposures, i.e., when D. magna is exposed to dietary Ni via living algae, and secondly, to quantify how nutritional quality shifts contribute to the toxic effects that are observed when algae are used as contaminated food vectors. For this aim, liposomes were prepared by the hydration of phosphatidylcholine in media containing 0 (control), 10, 50, 100 and 500mgNi/L. The liposome particles were then mixed with uncontaminated green algae in a 1/10 ratio (on a dry wt basis) to make up diets with constant nutrient quality and varying Ni contents (i.e., 1.2μgNi/gdry wt in the control and 18.7, 140.3, 165.0 and 501.6μgNi/gdry wt in the Ni-contaminated diet, respectively). A second food type was prepared on the basis of a 1/10 mixture (on a dry weight basis) of control liposomes and Ni-contaminated algae, representing a diet that differed in Ni content (i.e., 1.2, 26.8, 84.7, 262.3 and 742.7μgNi/gdry wt) and concentrations of essential nutrients (in terms of P and omega 3 poly-unsaturated fatty acids like eicosapentaenoic acid and α-linolenic acid). Both diets were then simultaneously fed to D. magna during a 21-day chronic bioassay, using reproduction, growth, survival, ingestion rate and Ni bioaccumulation as endpoints. Ni delivered by liposomes caused a significant inhibition of reproduction and growth when the metal accumulated to minimum levels of 11.9 and 20.0μgNi/gdry wt after 7 and 14 days, respectively. Using algae as Ni vector, similar effects of dietary Ni exposure occurred when algae had been pre-exposed to concentrations of at least 133μg/L of bioavailable Ni (i.e., Ni2+), which is similar to the reproductive EC50 of waterborne Ni exposure for D. magna (115μgNi2+/L). While this may have some consequences for predicting chronic Ni toxicity in this range of Ni concentrations with the biotic ligand model – which could be further improved by including the dietary toxicity pathway in this model, the occurrence of such high concentrations in the field is very rare. Hence, there seems to be very little environmental relevance for dietary Ni toxicity to D. magna. Finally, besides the direct effects of Ni there was no evidence that nutritional quality shifts could have affected daphnids’ growth, but it is very likely that the impairment of reproduction at toxic exposure levels of Ni was also partly the result of reduced fatty acid levels.

Temperature Depending Influence of the Martensite Formation on the Mechanical Properties of High‐Alloyed Cr‐Mn‐Ni As‐Cast Steels

AbstractThe temperature dependence of the martensite formation and the mechanical properties of three high alloyed Cr‐Mn‐Ni as‐cast steels with varying Ni contents were studied. The results showed that the Ms and Md temperatures of the steels decrease with increasing nickel contents. Therefore the strain‐induced martensite formation, the TRIP effect and the temperature anomaly of the elongations occurs at lower temperatures. The steel alloyed with 3% nickel shows a stress induced formation of martensite and a dynamic strain aging. Depending on the nickel content and the temperature a TWIP effect occurs additionally to the TRIP effect in the investigated steels. The study was performed by using static tensile tests, dilatometer tests, optical microscopy and the magnetic scale for the detection of ferromagnetic phase fractions.

Hydrogen gas sensing performance of Pd–Ni alloy thin films

We investigated the hydrogen (H 2) sensing properties of palladium (Pd)–nickel (Ni) alloy films with varying Ni content and discussed them in light of structural deformations. The Pd–Ni alloys operated reversibly upon H 2 absorption and desorption and their sensitivities decreased linearly with Ni content added to Pd. This was attributed to reduction in the lattice constant and interstitial volume caused by the Ni addition, allowing fewer hydrogen atoms to penetrate into the Pd–Ni alloy with higher Ni content. Interestingly, the response time of the Pd–Ni alloys was much shorter than that of pure Pd, presumably due to the fast permeation of hydrogen atoms through microscopic imperfections in the alloys. Unlike pure Pd, the Pd–Ni alloys showed an almost linear relationship between the sensitivity and H 2 concentration without hysteretic behaviors, enabling the detection of low concentration of H 2 down to 0.01%. These results provide a significant understanding of the role of Ni in the Pd–Ni thin films for improving the H 2 sensing properties of the Pd-based alloy film sensors.

A cornucopia of presolar and early solar system materials at the micrometer size range in primitive chondrite matrix

Abstract— We have used a variety of complementary microanalytical techniques to constrain the mineralogy, trace‐element distributions, and oxygen‐isotopic compositions in a 50 × 50 μm area of Acfer 094 matrix. The results reveal the exceptional mineralogical and compositional heterogeneity of this material at the sub‐μm level. We observe μm‐scale and sub‐μm grains with elemental associations suggesting feldspar, metal with widely varying Ni contents, and a Cr‐Fe alloy (in addition to forsterite, pyroxene, sulfide, ferrihydrite, and amorphous groundmass previously described). A new class of μm‐scale CAI (μCAI) is also observed, which show sub‐μm compositional zoning, and a range of oxygen isotopic compositions. Unlike the larger CAIs in Acfer 094, which are uniformly 16O‐enriched, two of the three μCAIs we analyzed are isotopically normal. We also observed a Li‐rich hotspot that detailed analysis by ToF‐SIMS suggests may be a LiCr‐oxide grain. Within the resolution of the NanoSIMS, this grain has isotopically normal Li. Finally, in our 50 × 50 μm area, we positively identified a presolar grain that is the most 18O‐rich silicate found so far in meteorites. The grain may originate from an asymptotic giant branch (AGB) star, or more likely, a supernova. In line with previous TEM studies (Greshake 1997), we find no evidence for clastic material (e.g., fragmental chondrules) in the matrix of Acfer 094: although the matrix is volatile‐depleted, this depletion does not appear to result from dilution of a primordial starting material with (depleted) chondrule fragments. Assuming that matrix experienced the depletion event, our data on the detailed mineralogy of Acfer 094 are currently equivocal in constraining the nature of that event. We observe carrier phases for several elements consistent with conditions approaching equilibrium condensation; however, the presence of an amorphous groundmass is suggestive of more rapid cooling.

High-pressure synthesis of novel hydride in Mg–Ni–H and Mg–Ni–Cu–H systems

Novel hydrides were synthesized in Mg–Ni–H and Mg–Ni–Cu–H systems by high-pressure technique using a cubic-anvil-type apparatus. Crystal structure and thermal stability of the hydrides were studied. The novel hydride with a composition of MgNi 2H y was synthesized at 973 K for 2 h under the pressure of over 2 GPa. This hydride could be synthesized from each starting material, such as MgNi 2(C36) and mixture of MgH 2– x mol% Ni ( x = 65–70). From fusion analysis, hydrogen content of the sample of MgH 2–67 at.% Ni prepared with hydrogen source at 973 K for 2 h under 5 GPa was estimated to be 2.23 mass% and chemical formula was corresponding to be MgNi 2H 3.2. The novel hydride was found to exhibit the body-centered tetragonal structure (space group I4/ mmm, No. 139) with lattice parameters of a = 0.327(3) nm, c = 0.878(9) nm. Moreover, crystal structure of novel hydride was distorted with varying Ni content, then it was found to exhibit C-faced based-centered orthorhombic structure (space group Pmmm, No. 47) with lattice parameters of a = 0.460(1) nm, b = 0.468(1) nm, c = 0.893(1) nm. In Mg–Ni–Cu–H system, crystal structure and thermal stability of Mg(Ni 1− x Cu x ) 2H y ( x = 0.05, 0.10, 0.15, 0.20) were investigated. The sample of Mg(Ni 0.95Cu 0.05) 2 prepared with hydrogen source at 973 K for 8 h under 5 GPa was dehydrogenated at 446 K, which is 15 K lower than that of MgNi 2H 3.2. Moreover, Mg(Ni 0.95Cu 0.05) 2 prepared with hydrogen source at 973 K for 2 h under 5 GPa,which did not react hydrogen sufficiently, was decomposed at 409 K.

Microstructural change in gravity cast Mg−Ni alloys with Ni contents

The effects of Ni content on the microstructures of gravity cast Mg−Ni alloys were examined. Different shapes of primary solid particles and microstructures of the eutectic matrix were observed with varying Ni content. The eutectic matrix in the hypoeutectic alloy consisted of rod-like Mg2Ni phase with a small amount of α-Mg phase. The eutectic matrix in the near-eutectic and hypereutectic alloys consisted of eutectic cells oriented in different directions. A transition of lamellae to fiber occurred. The formation of cellular structure and transition of lamellae to fiber resulted from two-phase instability in the coupled region induced by constitutional undercooling.

２１世紀における自動車部品の焼結材料技術 焼結低合金鋼の高性能化に向けたメゾヘテロ組織制御 第２報

In the previous report on the sintered low alloy steels (4600grade, 0.4mass%C) produced by MIM process varying Ni content from 0 to 8 mass%, the mechanical properties were improved significantly with increasing Ni content to 6mass%. This was attributed to the solution strengthening and the mezzo-heterogeneous microstructure which were consisted of Ni rich martensite surrounded by a network of tempered martensite. However, the tensile and fatigue strength of the steel added 8 mass% Ni were dropped by the increase of retained austenite. In this study, the effect of the different type of Ni powders on the mechanical properties of Fe-6Ni-0.5Mo-0.2Mn (mass%) was investigated to clarify and optimize the mezzo-heterogeneous microstructure.The tensile properties of the heat treated steels using the spherical Ni powder were lower than those using the spiky Ni powder. This seems to be due to the segregated distribution considerably of Ni rich phase and the decrease of Ni diffusion rate.

自動車部品に対するニーズの変化とこれに対応する焼結部品 焼結低合金鋼の高性能化に向けたメゾヘテロ組織制御

In our previous studies on the 4600 steels produced by Metal Injection Molding (MIM) process using mixed elemental powder, the fine heterogeneous microstructure caused by the agglomeration of Ni powders was reported to be significantly effective for the improvement of mechanical properties. This study has been performed to clarify and optimize the relationship between the mechanical properties and the heterogeneous microstructure for ultrahigh strengthening the sintered low alloy steels (4600grade, 0.4 mass%C) produced by MIM process varying Ni content from 0 to 8 mass%.The tensile and fatigue strength were improved significantly with increasing Ni content to 6mass%, without loss of the ductility. This seemed to be due to the solution strengthening and the mezzo-heterogeneous microstructure which were consisted of Ni rich martensite surrounded by a network of tempered martensite. However, the tensile and fatigue strength of the steel added 8 mass% Ni were dropped by the increase of retained austenite.

Effect of Mn and Ni on the Variation of the Microstructure and Mechanical Properties of Low-carbon Weld Metals.

Low-carbon weld metals with various amounts of Mn and Ni addition were made using metal-cored wires and Ar–2%O2 shielding gas, and their mechanical properties were evaluated. The objective of the research, aimed to develop welding consumables with better resistance to cold cracking, was to determine the optimum composition ranges of Mn and Ni, in the presence of carbon content less than 0.02%. The hardness of weld metals were found to increase linearly with Mn and Ni, which was attributed mainly to solid solution strengthening and in part to formation of hard phases. Varying Ni content influenced Charpy impact energy, the extent of which depended on Mn content. For a low-Mn composition, Ni addition increased hardness without sacrificing impact toughness whereas for a high Mn composition, Ni deteriorated the impact toughness seriously and caused intergranular fracture. The fracture path followed columnar grain boundaries that are identical to prior austenite grain boundaries since no d-ferrite phase formed during solidification. Accordingly, these boundaries without having ferrite phase were susceptible to cracking under dynamic loading. Based on hardness and impact resistance, the optimum levels of Mn and Ni were suggested to be 0.5–1% and 4–5%, respectively.

The Role of Ni in the Formation of Low Resistance Ni–Ge–Au Ohmic Contacts to n+ GaAs Heterostructures

Nickel is a commonly used wetting agent in alloyed Au–Ge ohmic contacts to n-GaAs, resulting in uniformity improvements to the morphology and contact resistance. In order to study the role of Ni in Ni–Ge–Au alloys, we have fabricated samples with varying Ni content and characterized them using electron microbeam techniques. Our data indicate the amount of Ni in the alloy affects the microstructure and composition, the morphology of the metal/GaAs interface, and the amount of GaAs consumed during the alloy reaction. Also, the dopant distribution into the GaAs is heterogeneous depending on the alloy microstructure.

Fluidization of cryogels in a conical column

Hydrodynamic studies of NiO/Al 2O 3 cryogels (Group-C particles) with varying Ni contents in a cylindrical column indicated poor gas fluidizability, characteristic of cohesive powders. In order to improve the fluidizability of a 14% NiO/Al 2O 3 cryogel, a conical column was designed and employed. Experiments showed that above a critical inlet gas velocity (0.44 m/s), the entire bed fluidized in a state of perfect mixing. Reduction of the gas velocity down to a value of 0.33 m/s caused a segregated bed containing agglomerates (2 mm diameter) in a cylindrical core and clusters (0.33 mm diameter) in the surrounding annulus. A modified Ergun equation was developed to predict the packed bed pressure drop and the minimum fluidization velocity at the inlet of the conical bed. Both correlations were applied to the conical packed bed using a proposed core-annulus model which characterizes the bed composed of the binary particle mixture. The model correlations were validated using experimental data. Analysis of kinetic data supports conclusions made from the hydrodynamic study.

Dependence of radiation-induced segregation on dose, temperature and alloy composition in austenitic alloys

Radiation-induced segregation (RIS) of austenitic stainless steels was investigated using proton irradiation. Dose and temperature dependence of RIS was determined by irradiation of an Fe 20Cr 24Ni alloy over a range of doses and temperatures. Four additional alloys were included to create three alloy series of either constant Ni or constant Cr to identify bulk composition effects on RIS. Measurements of grain boundary composition were made using Auger electron spectroscopy of grain boundary facets exposed in situ. Results showed that over the dose range 0.1 to 3 dpa grain boundary Ni increased and Cr decreased sharply below 1 dpa and achieved near-saturation between 1 and 3 dpa. Segregation increased from 200 to 500°C, and it did not appear to have saturated by 500°C. For a constant bulk Ni content and for increasing bulk Cr content, grain boundary Cr increases and Ni decreases. For constant bulk Cr content and increasing Ni, grain boundary Cr decreased and Ni increased. Dose and temperature dependence agreed well with Perks' model in trends but not in magnitudes, as did the alloy dependence for the case of fixed bulk Cr and varying Ni content. The dependence of grain boundary Ni on bulk Cr/Ni was opposite that predicted by Perks' model considering only the inverse Kirkendall mechanism. Agreement between measured and model results was achieved by accounting for the composition dependence of the atom-vacancy exchange frequency and the correlation coefficient for diffusion.

Thermodynamics of ternary Fe-Ni-N-austenites

Measurements, in the range 1140–1548 K, of the temperature variation of the solubility of nitrogen at constant pressure (1.04 × 10 5 Pa) in Fe-Ni fee solid solutions in equilibrium with N 2 gas, show that the partial molar enthalpy H i of the nitrogen atoms is invariant to the nickel concentration up to 15 atm % Ni. In the same temperature range the partial molar excess entropy S xs i exhibits a slight decrease with increasing nickel concentration. The thermodynamic data are consistent with the cell model for ternary solid solutions in which the nickel atoms create shallow trapping sites for N-atoms, deeper by only 4.9 kJ/mol than interstitial sites in binary Fe-N solutions. The variation in H i with nickel content due to the distribution of N atoms in energetically differing cells is of about the same size, but opposite in sign, to the contribution to H i ascribable to the change in specific density of the substitutional lattice with varying Ni content.

Resistance Changes in Iron-Base Alloys Forming Ni3(AI Ti) Precipitates

The resistivity of Fe-Ni-Cr solid solutions increases and the temperature coefficient decreases with rise in nickel content. This explains the peculiarity observed in γ′-forming stainless steels of a resistance increase on ageing that is greater when measured at the ageing temperature than at a low temperature. A range of steels with varying Ni content and Ti/Al ratio has been examined and the anomalous resistivity increase calculated. This is shown to be independent of temperature within the accuracy of the experiments and to decrease slowly with increase in γ′ size, but some effect remains at particle sizes of 25–30 nm dia. Cold work lowers the resistivity of Fe-Ni-Cr alloys with high Ni content and a rapid increase occurs on annealing at 500°C (773 K). A similar effect is observed in the high-nickel γ′ - forming alloys and is thought to be due to short-range order in the matrix.