Increasing Ni Addition Research Articles

The role of nickel in cadmium accumulation in rice

Rice is one of the world's staple foods. Cadmium (Cd) levels in paddy soil are still increasing, and “Cd-contaminated rice” is a frequent occurrence, posing a serious threat to human health. Therefore, Cd contamination in rice is a key issue in agricultural production that needs to be addressed urgently. The Cd accumulation in rice is closely related to other elements. In this study, the impact of nickel (Ni) on the uptake and accumulation of Cd in rice was revealed, and the mechanism was discussed. Statistical analysis of field data showed that Cd concentration in rice grains decreased exponentially with increasing Ni concentration in paddy soils, which was verified by the hydroponic experiments. Under 5 μmol/L Cd exposure conditions, the addition of Ni (100 μmol/L) reduced the Cd contents in roots, stems, and leaves by 81.6 %, 60.6 %, and 65.9 %, respectively. With the presence of Ni, the amount of iron plaque decreased, and the Cd content in the iron plaque was reduced due to the competition between Ni and Cd for adsorption sites. In addition, the migration of Cd from stems to leaves was reduced. At the same time, the distribution of Cd in the cell was altered, and the concentration of Cd in the root cell walls increased with increasing Ni addition under 5 μmol/L Cd exposure. These findings highlight the critical role of Ni in inhibiting Cd accumulation in rice, and provide important information for understanding the effects of coexisting elements in Cd-contaminated soils on Cd accumulation in crops.

Study of the intrinsic mechanisms of nickel additive for grain refinement and strength enhancement of laser aided additively manufactured Ti–6Al–4V

It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing (AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing (LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy. (a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and 1.46, respectively. (b) Ni additive can discernibly induce the formation of globular α phase, which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to 2.5 wt. %. (c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–xNi alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.

Atomic-level understanding of weakening crystallization in additive manufactured ternary Fe-based metallic glasses with Ni addition

The almost inevitable crystallization is a key hindrance to the excellent performance of additive manufacturing (AM) fabricated Fe-based metallic glasses (FMGs). Considering the role of chemical composition in glass-forming ability, ternary FMGs FeCuNi were selected to study the crystallization mechanism at an atomic level. The high inclination of crystallization in AM-fabricated FeCuNi FMG was obviously inhibited with increasing Ni addition until 30%, which lies in the decreasing emerging body-centered cubic phases, is correlated to the decreasing crystal bond pairs 1661 and 1441 and correspondingly decreasing Voronoi polyhedrons 〈0, 6, 0, 8〉 and 〈0, 5, 2, 6〉. Meanwhile, the weakening crystallization is also indicated by the increasing amorphous phases such as the icosahedron and icosahedral-like polyhedrons. This work helps better understanding the weakening crystallization in AM-fabricated ternary or multi-component alloys, which is very important for achieving complex geometry FMG parts with less crystallization and, in turn, excellent performance by AM technique.

High temperature oxidation behaviour of γ′-strengthened Co-based superalloys with different Ni addition

High temperature oxidation behaviours of γ′-strengthened Co-based superalloys with various Ni additions were investigated at both 800 °C and 900 °C. The results show that the superalloys show excellent oxidation resistance due to the formation of compact spinel oxide scales. With the increasing of Ni addition, the concentration of Cr in scale/alloy interface will be increased but that of Co will be decreased. And the growth of Cr2O3 will be promoted, while CoO nucleation will be hindered. Therefore, increasing Ni addition helps the formation of protective spinel oxide scales and delays nodular oxidation, which favours to be better oxidation resistance.

Investigations of the nickel promotional effect on the reduction and sintering of tungsten compounds

In this article, Ni-coated W powders were firstly prepared by a liquid-solid doping method combined with air calcination and hydrogen reduction. X-ray diffraction analysis, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and temperature programmed reduction analysis were carried out to investigate the nickel doping process in WO3 and its influence on the reduction behaviors of tungsten oxides. It reveals that after calcinations most Ni ions would occupy the lattice sites of host W ions and decrease the interplanar spacing of WO3. The latter is due to the promotion of oxygen vacancy generation within WO3 rather than the changes in ionic radius. After hydrogen reduction, the doped Ni atoms precipitate onto the surface of W particles as thin metallic coatings, whereby the size and morphology of reduced W particles are varied greatly with increasing Ni addition. The presence of Ni has also been found to lower the reduction barriers for WO3 by using first-principles calculation. Finally, W-Ni compacts were sintered at 1500 °C in hydrogen atmosphere and the accelerated densification phenomenon of W alloy upon Ni doping is discussed.

Microstructure and hardness of SAC305-xNi solder on Cu and graphene-coated Cu substrates

This study investigated the interfacial reaction, the microstructure, and the hardness of the SAC305-xNi solder on both Cu and graphene-coated Cu (G–Cu) substrates. The experimental results indicate that the increase of Ni content in the solder leads to the roughness of the (Cu, Ni)6Sn5 IMC layer on Cu. In contrast, the growth of the (Cu, Ni)6Sn5 interfacial IMC, which results from increasing Ni addition, is significantly suppressed on G–Cu substrates. As the concentration of Ni ranges from 0 to 0.2 wt%, the microstructure of the solder bulks on Cu substrates shows slight changes. The hardness of the solder bulks in SAC305-Ni/Cu is similar to that in the SAC305/Cu solder joint. The amount of β-Sn rises and the eutectic area shrinks due to increasing Ni addition in the solder bulks on G–Cu substrates. Therefore, the solder bulks in the SAC305-Ni/G–Cu show lower hardness than that in the SAC305/G–Cu solder joint.

Proton Conductivity of Ni, Y Co-Doped BaZrO<sub>3</sub>

Dense sintered bodies of proton conducting BaZrO3 (BZ) and Y-doped BaZrO3 (BZ-Y) were obtained at 1600℃ for a short sintering time of 5 hours, by the addition of NiO as a sintering promotion agent. The relative density and grain growth of samples, Ni-doped BaZrO3 (BZ-N) and Ni, Y co-doped BaZrO3 (BZ-NY), were increased with increasing Ni addition. The sinterability of BZ-NY was greatly improved just to add only 0.6 mol% Ni and the relative density of this sample was more than 98%, in contrast to that of 60% at most for BZ-Y without Ni addition. Electrical conductivity of BZ-NY added Ni 1.0 mol%, BaZr0.91Ni0.01Y0.08O3-α, was more than 10-3 S.cm-2 at 900℃ in a wet 1% hydrogen atmosphere, which value was 10 times higher than that of BZ-Y. In addition, the kind of electrical conduction carrier and an ionic transport number were also examined by employing various concentration cells. It was found that the proton conduction was dominant for both BZ-N and BZ-NY samples, although BZ-NY showed scarcely oxygenion conduction approximately 10% in a high temperature range higher than 800℃. From these results, as mall amount of Ni addition found to be effective for improvement of both the sinterability and the electrical conductivity.

The effect of Ni addition on microstructure and soft magnetic properties of FeCoZrBCu nanocrystalline alloys

(Fe0.7Co0.3-xNix)88Zr7B4Cu1 nanocrystalline alloys were developed with the aim of improving the magnetic properties while keeping high Curie temperature (TC). It was revealed that Ni addition inhibited the precipitation of metastable fcc-(Fe,Co,Ni) phase hence increased thermal stability. Although the saturation magnetic flux density (Bs) showed a slight decrease, uniform nanostructure with small grain size and high volume fraction of crystals was formed with increasing Ni addition. As a result, the (Fe0.7Co0.3-xNix)88Zr7B4Cu1 nanocrystalline alloys exhibited excellent magnetic properties with a high Bs of 1.54-1.79 T, low coercivity (Hc) of 17-20 A/m and low core loss of 9.1-11.1 W/kg at 1 T and 400 Hz. The combination of high TC of 747-972 °C, low core loss as well as low material cost promised this FeCoNiZrBCu alloys broad application prospect at high temperature.

Microstructure and mechanical properties of as-cast Mg-8Sn-1Al-1Zn-xNi alloys

Mg-8Sn-1Al-1Zn-xNi (x=0.5%, 1.0%, 1.5%, 2.0%, mass fraction) alloys were designed and prepared. The microstructures and the mechanical properties were studied by using optical microscope, scanning electronic microscope, energy dispersive X-ray spectroscope, X-ray diffraction and a standard universal testing machine. The results show that the microstructure of Ni-containing alloys consist of α-Mg, Mg2Sn, β-Mg-Ni-Al and γ-AlNi phases. No β-Mg-Ni-Al phase was observed in TAZ811-2.0Ni alloy due to its 1:1 atomic ratio of Ni/Al. The addition of Ni refines the α-Mg dendrites and suppresses the formation of coarse Mg2Sn phase. The tensile properties results show that the TAZ811-0.5Ni alloy presented the best mechanical properties, which is due to the rod-like β-Mg-Ni-Al phase, refined α-Mg dendrites and Mg2Sn phase, as well as γ-AlNi phase. The tensile fracture mechanism transits from cleavage to quasi-cleavage fracture with the increasing Ni addition.

Enhanced ductility and mechanical strength of Ni-doped Sn–3.0Ag–0.5Cu lead-free solders

In this paper, the tensile tests were conducted to investigate the effect of adding a small amount of Ni on the microstructure, thermal and mechanical properties of 3.0Ag–0.5Cu(SAC 305) solder. The results indicated that addition of Ni can effectively decrease both the undercooling and the onset melting temperature of SAC(305) solder alloy. The strength and ductility of the SAC(305) solder depend significantly on Ni content. In general, the SAC(305)–0.5%Ni solder reveals superior mechanical properties in terms of maximum strength and ductility when compared to the high Ni-content or plain solders. Microstructure analysis revealed that a new η-(Cu,Ni)6Sn5 intermetallic compound (IMC) phase containing large amount of Ni was generated, while the initial Cu6Sn5 phase was converted into (Cu,Ni)6Sn5 phase after 0.5%Ni addition. Besides, the fine fiber-like Ag3Sn and finer dot-shaped precipitates rather than needle-like morphology have occurred at the surface of β-Sn matrix easily, which could provide more obstacles for dislocation pile up in the adjacent grains and enhanced the mechanical property. With increasing Ni addition, the Ni-doped SAC(305) solder showed a corresponding deterioration in their mechanical property due to the coarsening of (Cu,Ni)6Sn5 IMCs and increasing the inter-particle spacing of Ag3Sn IMCs in the eutectic colony.

Effects of Ni addition on the microstructure and compressive deformation behavior in Zr–Cu–Ni martensitic alloys

Bulk Zr 50Cu 50− x Ni x ( x = 5, 10, 15, 20, and 25) martensitic alloys with high strength, good ductibility and strong work-hardening ability have been prepared by copper-mold-casting. With the increase in the Ni content, the grain size of the ZrCu martensite becomes finer, the yield strength of the alloy increases, while the ultimate compressive strength and fracture strain first increase and then decrease. The Zr 50Cu 35Ni 15 ( x = 15) alloy exhibits the highest ultimate compressive strength of 1916 MPa, the largest fracture strain of 12.85% and the work-hardening capacity of 0.83. The work-hardening behavior of these alloys depends on the Ni content. The solid solubility of Ni in matrix influences the dislocation density in the as-cast sample. As a result, the work-hardening capacity of Zr 50Cu 50− x Ni x martensitic alloys decreases with increasing Ni addition.

Effects of Ni addition on the interfacial reactions between Sn–Cu solders and Ni substrate

This research investigates the effects of adding a small amount of Ni to solder. The interfacial reactions between Ni and the Sn–Cu solders at 250 °C are examined. Two sets of Sn–0.7 wt% Cu– xNi solders and Sn–1.0 wt% Cu– xNi solders ( x = 0.02, 0.05 and 0.1 wt%) were prepared. The results reveal that the interfacial reactions are very sensitive to Ni. With increasing Ni addition, the reaction phase grain, Cu 6Sn 5, becomes larger and its morphology changes from a rod-like shape into a faceted structure. The reaction progressions are accelerated in comparison with those without Ni addition. The solder spreading effect on the Cu 6Sn 5 morphology was also investigated. Cu 6Sn 5 exhibits a gradual change in microstructure from the center to the rim for the case when the solder ball spreads over a Ni substrate. However, the solder does not alter the Cu 6sn 5 microstructure while reacting on a small Ni pad without spreading. This suggests that the Cu and Ni contents in the solder near the interface vary during the solder ball spreading process.

Application of multi-walled carbon nanotubes as efficient support to NiMo hydrotreating catalyst

The feasibility of multi-walled carbon nanotubes (MWCNTs) as support to NiMo catalysts for hydrotreating of gas oil derived from Athabasca bitumen was tested in a trickle bed reactor at industrial conditions. High quality MWCNTs were prepared by CVD method using ferrocene as catalyst and toluene as carbon source. The produced MWCNTs were characterized by XRD, TEM, TGA and Raman spectroscopy in order to reveal the morphological and structural characteristics. Using functionalized MWCNTs as support, NiMo catalysts were prepared with varying Ni and Mo content by pore filling impregnation method. The calcined NiMo/MWCNTs catalysts were characterized by ICP-MS, N2 adsorption, XRD and TPR and the sulfide form of the catalysts was examined by DRIFT spectroscopy of adsorbed CO. The XRD patterns confirm the enhanced dispersion of MoO3 particles when increasing the Ni content from 0 to 4.5 wt.% over 12 wt.% Mo/MWCNTs. The TPR profiles indicate the two step reduction characteristics of Mo6+ to Mo in lower oxidation state such as Mo4+ and Mo0. The promoted and unpromoted MoS2 sites were clearly differentiated with the help of DRIFT of adsorbed CO over sulfided catalysts. The number of Ni promoted MoS2 (NiMoS phase) sites is increased significantly with increasing Ni addition up to 3 wt.% over 12 wt.% Mo/MWCNTs. The HDN and HDS activities of sulfided NiMo/MWCNTs using bitumen derived light gas oil were carried out at different temperatures under industrial condition. The HDN and HDS activities of the catalysts increased with increasing Ni content up to 3 wt.% and Mo content up to 12 wt.%. Based on weight of the catalyst, the HDN and HDS activities of 3 wt% Ni–12 wt.% Mo/MWCNTs are significantly higher than those over conventional Al2O3-based catalyst under the experimental conditions studied. The introduction of 2.5 wt.% P to MWCNTs-based catalyst found to show a fall in hydrotreating activity.

Hydroisomerization of ethylbenzene over bimetallic bifunctional zeolite catalysts

Zeolite-β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3, 0.5 wt.%) amount of Ni. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. The TEM analysis indicates that the average metal particle size increases with increasing Ni addition. The states of Ni and Pt were analyzed by ESCA. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show the occupation of some of the acid sites by the added Ni species. Ni addition up to 0.3 wt.% over 0.1 wt.% Pt/H-β and 0.1 wt.% over 0.1 wt.% Pt/H-MOR enhances the ethylbenzene conversion, isomerization selectivity and sustainability of the catalysts. Further Ni addition above the threshold value leads to a drastic drop in activity and isomerization selectivity. Zeolite-β-based Ni–Pt catalysts always show higher activity and selectivity than mordenite-based catalysts.

WEAR AND HEAT CHARACTERIZATION OF BOTH THE AS-CAST AND HEAT EXPOSED SPECIMENS FOR AL/SiC PARTICULATE COMPOSITES

This Study is to investigate on the wear characterization and heat resistance of aluminum/silicon carbide (Al/SiC) with different particles (3, 5, and 10 μm) composites manufactured by duplex process, which consists of squeeze-infiltration and squeeze casting. Also, this study is to investigate the effect of alloying element (Ni) on the microstructure, wear behavior and heat resistance of Al/SiC composite. Owing to the increase in interfacial area between SiC particles and matrix in both the as-cast and heat exposed specimens (at 250 oC and 350 oC for 5hr), the decrease in nano-SiC particles size resulted in the increase in the hardness of composites. And in case of 3 μm SiC reinforced Al composites as compared with other composites, the highest density of dislocation was generated during manufacture. Composite with 3μm SiC has the lowest wear amount among composites reinforced with 5 and 10μm SiC. Heat resistant property was improved with increasing Ni addition content (wt.) in Al/SiC composites. The wear resistance at 200 oC in argon gas on composite was greater than those at 200 oC and room temperature in the as-composites.

Shear strength and interfacial microstructure of Sn–Ag– xNi/Cu single shear lap solder joints

This study investigates composite lead-free solders fabricated by adding between 0.5 and 3 wt% of Ni particles in situ to Sn–3.5 wt%Ag lead-free solder. The single lap shear strength, fracture behavior and microstructural evolution characteristics of the as-reflowed specimens are examined and compared with those of specimens thermally aged at 150 °C for various aging times. In general, it is found that the single lap shear strength of the joints increases with increasing Ni addition in the as-reflowed condition, but decreases with increasing storage time in the aged specimens. For Ni additions of 0.5 and 1 wt%, the specimens fracture in the solder near the intermetallic compound (IMC) layer/solder interface, which suggests that the solder matrix has a lower strength than the IMC layer. The presence of elongated dimple-like structures on the fracture surfaces of these specimens is indicative of a ductile failure mode. For Ni additions of more than 1 wt%, the specimens fracture with brittle characteristics at the solder/IMC interface, which indicates that an increased Ni addition increases the strength of the solder matrix beyond that of the interfacial layer.

Hydroisomerization of ethylbenzene over bimetallic bifunctional zeolite catalysts: Maximization of xylene production

Zeolite-β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3, 0.5 wt.%) amount of Ni and reduced at 475 °C. The line broadening in the XRD patterns reveals that the increasing Ni addition decreases the crystallinity of zeolites. The catalysts were also characterized by TEM, ESCA and TPD of ammonia and pyridine. The TEM results show that the average metal particle size increases with increasing Ni addition. ESCA studies clearly points to the maximum percentage of Ni reduction in the Pt loaded zeolite-β and mordenite catalysts. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show that the number of the acid sites of the catalysts decreases upon the addition of the Ni species. Hydroisomerization of ethylbenzene over the Pt–Ni loaded zeolite and mordenite was carried out in the temperature range 250–400 °C. It has been found that the addition of Ni up to 0.3 wt.% over 0.1 wt.% Pt loaded zeolite-β and 0.1 wt.% over 0.1 wt.% Pt loaded mordenite greatly enhances the ethylbenzene conversion, isomerization selectivity and sustainability of the catalysts. Further addition of Ni above the threshold value leads to a drastic reduction in the activity and isomerization selectivity. Zeolite-β-based Ni–Pt catalysts show higher activity and selectivity than mordenite-based catalysts under the optimized reaction conditions.

Ni–Pt/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

Ni–Pt/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt/H-Y and further addition leads to the occurrence of unreduced nickel species as NiAl2O4. A TEM study shows the formation of bimetallic (Ni–Pt) particles of nanoscale size and the average particle size is found to increase with increasing Ni loading. Acidity measurements by NH3-TPD and pyridine-adsorbed FT–IR spectroscopy show the increasing occupation of acid sites by increasing nickel loading. The catalytic activity of Ni–Pt/H–Y zeolite and Pt/H–Y catalysts was compared and it was found that addition of Ni up to 0.3 wt.% increases conversion of toluene and 1,2,4-trimethylbenzene, disproportionation selectivity and sustainability of the catalysts. Further addition of Ni leads to a decrease in conversion and disproportionation selectivity and increasing dealkylated products, which may be due to the presence of unreduced Ni species and pore blockage by large-sized bimetallic particles formed.

Ni–Pt loaded silicoaluminophosphate molecular sieves for hydroisomerisation of n-heptane

Silicoaluminophosphates SAPO-5 and SAPO-11 were hydrothermally synthesised and loaded with 0.2 wt.% Pt and varying (0, 0.2, 0.4 and 0.6 wt.%) amount of Ni. The line broadening XRD and TEM analyses of Ni–Pt/SAPOs indicate that the average size of Ni–Pt particles increases with increasing Ni addition. The ESCA studies reveals that complete reduction of Ni is observed only up to 0.4 wt.% Ni addition. The acidity of the catalysts analysed by TPD of ammonia revealed that added Ni species occupy the acid sites of SAPOs. Catalysts 0.4 wt.% Ni and 0.2 wt.% Pt loaded SAPOs show enhanced activity in n-heptane conversion, isomerisation selectivity and stability of the catalysts. Further, the selectivity towards the multibranched (MTB) isomers by protonated cyclopropane (PCP) intermediate formation is enhanced over the above catalysts. SAPO-5 based Ni-Pt catalysts show better activity than SAPO-11 based catalytic systems.

Activity, selectivity and stability of Ni–Pt loaded zeolite-β and mordenite catalysts for hydroisomerisation of n-heptane

Zeolites β and mordenite were impregnated with 0.1 wt.% Pt and varying (0, 0.1, 0.3 and 0.5 wt.%) amount of Ni and reduced at 475 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. The TEM analysis indicates that the average metal particle size increases with increasing Ni addition. The states of Ni and Pt were analysed by ESCA. The acidity measurements by both TPD of ammonia and pyridine adsorbed FT-IR spectroscopy show the occupation of some of the acid sites by the added Ni species. Hydroisomerisation of n-heptane was carried out in the temperature range 225–375 °C and found that Ni addition up to 0.3 wt.% over 0.1 wt.% Pt/H-β and 0.1 wt.% over 0.1 wt.% Pt/H-MOR enhance the n-heptane conversion, isomerisation selectivity and sustainability of the catalysts. Also, the multibranched (MTB) isomers selectivity and protonated cyclopropane (PCP) intermediate mechanism are favoured over the above catalysts. Further Ni addition above the threshold value leads to fall in activity and isomerisation selectivity drastically. Zeolite-β based Ni-Pt catalysts always show higher activity and selectivity than mordenite based catalysts.