Ni Counterparts Research Articles

Deposition-based synthesis of nickel-based superalloy microlattices

Nickel-based superalloy microlattices with periodic hollow struts were fabricated through a combination of two deposition-based methods - electrodeposition and pack cementation - via the following steps: (i) creating a template by self-propagating photopolymer waveguide prototyping, (ii) coating the template with nickel by electroplating, (iii) etching away the template, (iv) coating the Ni lattice with Cr, Al, and Ti by pack cementation, (v) diffusing the Cr, Al, and Ti rich coatings into the nickel to achieve a homogenized alloy and (vi) optionally, aging the alloy to create γ′-precipitates. The resulting nickel-based superalloy microlattices are 2–4 times stronger than pure Ni counterparts.

Dual effects of co-electrodeposition of CeO2 nanoparticles on the grain growth of nanocrystalline Ni matrix

Abstract

Age affects not only metabolome but also metal toxicity in Scenedesmus quadricauda cultures

Responses of Scenedesmus quadricauda grown in vitro and differing in age (old culture—13 months, young culture—1 month) to short-term cadmium (Cd) or nickel (Ni) excess (24h) were compared. Higher age of the culture led to lower amount of chlorophylls, ascorbic acid and glutathione but higher signal of ROS. Surprisingly, sucrose was detected using DART-Orbitrap MS in both old and young culture and subsequent quantification confirmed its higher amount (ca. 3-times) in the old culture. Cd affected viability and ROS amount more negatively than Ni that could arise from excessive Cd uptake which was also higher in all treatments than in respective Ni counterparts. Surprisingly, nitric oxide was not extensively different in response to age or metals. Strong induction of phytochelatin 2 is certainly Cd-specific response while Ni also elevated ascorbate content. Krebs cycle acids were more accumulated in the young culture but they were rather elevated in the old culture (citric acid under Ni excess). We conclude that organic solid ‘Milieu Bristol’ medium we tested is suitable for long-term storage of unicellular green algae (also successfully tested for Coccomyxa sp. and Parachlorella sp.) and the impact of age on metal uptake may be useful for bioremediation purposes.

Synergistic catalysis of MCM-41 immobilized Cu–Ni nanoparticles in hydrolytic dehydrogeneration of ammonia borane

Bimetallic Cu–Ni nanoparticles (NPs) were successfully immobilized in MCM-41 using a simple liquid impregnation-reduction method. All the resulting composites Cu–Ni/MCM-41 catalysts with various contents of Cu–Ni, and in particular Cu0.2Ni0.8/MCM-41 sample, outperform the activity of monometallic Cu and Ni counterparts and pure bimetallic Cu0.2Ni0.8 NPs in hydrolytic dehydrogeneration of ammonia borane (AB) at room temperature. The Cu0.2Ni0.8/MCM-41 catalyst exhibits excellent catalytic activity with a total turnover frequency (TOF) value of 10.7 mol H2 mol catalyst−1 min−1 and a low activation energy value of 38 kJ mol−1 at room temperature. In addition, Cu0.2Co0.8/MCM-41 also exhibits excellent activity with a TOF value as high as 15.0 mol H2 mol catalyst−1 min−1. This obtained activity represents the highest catalytic active of Cu-based monometallic and bimetallic catalysts up to now toward the hydrolytic dehydrogeneration of ammonia borane (AB). The unprecedented excellent activity has been successfully achieved thanks to the strong bimetallic synergistic effects among the Cu–Ni (or Co) NPs of the composites.

Facile surfactant-free synthesis of monodisperse Ni particles via a simple solvothermal method and their superior catalytic effect on thermal decomposition of ammonium perchlorate

Successful synthesis of monodisperse nickel particles with narrow particle size distributions is reported for the first time via a simple solvothermal method with ultrasonic treatment using no surfactants. The Ni products are characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The as-synthesized monodisperse Ni particles show a spherical morphology with the mean particle size of 46.2, 60.1 and 113.7 nm for the reaction time of 0.5, 1 and 3 h, respectively at a low temperature of 100 degrees C. The catalytic effect is investigated for the Ni particles on the thermal decomposition of ammonium perchlorate (AP) using differential thermal analysis and thermogravimetry. For the purpose of comparison, as-prepared and commercial non-monodisperse Ni particles are used for examining the catalytic effect. The monodisperse Ni particles show a superior catalytic effect over the non-monodisperse Ni counterparts with a similar mean particle size. The surface areas of Ni particles are measured by Brunauer-Emmett-Teller (BET) technique. A theoretical consideration is also presented for analysis of the surface areas of monodisperse and non-monodisperse particles. Both the BET and theoretical results show that the surface area of monodisperse particles is higher than that of non-monodisperse counterparts. Consequently, the catalytic effect of Ni particles on thermal decomposition of AP is explained in terms of the surface areas.

Effects of saccharin and cobalt concentration in electrolytic solution on microhardness of nanocrystalline Ni–Co alloys

Cobalt content, surface morphology and microhardness of nanocrystalline Ni–Co deposits prepared by pulse plating technique at constant electrodeposition conditions with varied concentration of saccharin and cobalt sulfate in the electrolyte were investigated. It is found that appropriate amount of both additions could lead to finer structure and higher hardness of the deposit and further increase of the concentration could result in decline of the hardness, which is regarded as the result of inverse Hall–Petch relation. The maximum hardness of the Ni–Co alloy deposits is not higher than that of their pure Ni counterparts, indicating that the refinement hardening effect (Hall–Petch relation) is dominant in nanocrystalline Ni–Co alloy deposits. By adding Co ions to the electrolyte, the amount of organic refiner saccharin (responsible for introduction of sulfur and carbon impurities) needed to produce nanocrystalline deposits could be remarkably reduced.

Dopant Segregated Pt and Ni Germanosilicide Schottky S/D p-MOSFETs with Strained Si-SiGe Channel

Dopant segregated Pt and Ni germanosilicide (PtSiGe and NiSiGe) Schottky source/drain (S/D) transistors were demonstrated on Si1-xGex substrates. The Schottky barrier height of Pt-Si0.7Ge0.3 was decreased by 0.2 eV compared to Pt- Si due to the smaller band-gap of SiGe and the dopant segregation effect. Schottky p-MOSFETs with Pt germanosilicided S/D junctions and strained Si/SiGe channels have also been demonstrated with 65 % higher drive current and lower leakage current compared with their Ni counterparts.

The Influence of the Alkyl Chain Length on Extraction Equilibrium of Cu(II) Complexes with 1‐Alkylimidazoles in Aqueous Solution/Organic Solvent Systems

The partition of Cu(II) complexes with 1‐alkylimidazoles (with alkyl ranging from 1‐n‐butyl through 1‐n‐hexadecyl) between the aqueous ((0.5HL, K)NO3) and organic phase has been studied at 25°C. The organic solvents used were toluene, p‐xylene, tetrahydronaphthalene, dichloromethane, 2‐ethyl‐1‐hexanol, and others. Extraction curves have been shown to be displaced towards lower pH values with increasing alkyl chain length of the alkyl substituent. Stability constants of the Cu(II) complexes with the 1‐alkylimidazoles have been determined in the aqueous phase as well as the number of compounds extractable into the organic solvent, and their partition ratios. Stability constants of the complexes did not depend on the alkyl chain length. One or two complexes were transferred to the organic phase. Partition ratios of these complexes, P 1 and P 2, increased rapidly with increasing alkyl chain length. They were higher in magnitude than those of their Co(II), Ni(II), and Zn(II) counterparts.

Hydrogen production by oxidative reforming of hexadecane over Ni and Pt catalysts supported on Ce/La-doped Al 2O 3

The activity and selectivity to hydrogen of alumina-supported nickel or platinum catalysts doped with Ce and La for the oxidative reforming of hexadecane were studied. The influence of both thermal stabilizer and activity promoter, such as lanthanum and cerium oxide, respectively, over hydrogen yield and catalyst durability was investigated. Catalytic activity was found to depend strongly on the type of metal, platinum showing lower specific activities per atom of metal exposed and a higher selectivity to combustion products than the Ni counterparts. The characterization results achieved with H 2 chemisorption, XRD, TPR and XPS showed differences in surface metal concentrations and metal–support interactions which depend on the presence of cerium and/or lanthanum in the support composition. For both based metal catalysts higher reforming activities were found when active metals were deposited on Ce–La–Al 2O 3 substrate. For Pt-based catalysts, the increase in activity observed for the sample using Ce–La-modified alumina as support is suggested to be related with a participation of lanthanum in the reaction more than modifications on coke resistance or dispersion and state of platinum-induced by lanthanum. In the case of Ni-based catalysts, a lower carbon deposition and a higher thermal stability of metallic Ni particles under reaction conditions were observed for catalyst using Ce–La-modified alumina as support. It is suggested that the higher number of Ni–Ce and Ni–Al surface interactions developed Ce–La–Al 2O 3-supported Ni catalysts are responsible of the better catalytic behaviour of this sample in the oxidative reforming of hexadecane.

Remote Substituents Controlling Catalytic Polymerization by Very Active and Robust Neutral Nickel(II) Complexes

More than 70 million tons of polyethylene and polypropylene are produced annually. The majority is prepared by catalytic polymerization employing Ziegler or Phillips catalysts based on early transition metals. More recently, olefin polymerization by complexes of late transition metals has also received increasing attention. A major motivation is their higher tolerance towards polar reagents due to a reduced oxophilicity by comparison to early transition-metal catalysts. Thus, ethylene and 1-olefins can be copolymerized with acrylates in a random fashion, and ethylene homoand copolymerizations can be carried out in aqueous emulsion to afford polymer latexes (i.e., aqueous dispersions of polymer particles of about 50–1000 nm size). The discovery by Brookhart and co-workers of the unique catalytic properties of cationic nickel and palladium diimine catalysts in olefin polymerization has given a strong impulse to the field. As a result, polymerization with neutral Ni complexes has received renewed interest, as these catalysts are expected to be more functional-group tolerant than their cationic Ni counterparts. However, catalyst activity and stability over time and the capability to form polymers with higher molecular weights at the same time are critical issues, particularly if the effort for catalyst synthesis is also considered. By analogy with the influence of bulky alkyl or aryl groups in cationic diimine complexes, in neutral Ni kN,O salicylaldiminato complexes bulky isopropyl groups on theN-aryl moiety retard chain transfer, which is supported by computational studies by Ziegler and co-workers. Introduction of electron-withdrawing substituents in the ortho or para position of the O donor in neutral nickel(ii) complexes has been reported to increase catalytic activities substantially, again in accordance with theoretical calculations. Most specifically for this class of catalysts, Grubbs and co-workers have shown that bulky groups in the C3 position of the Ocoordinating phenolate moiety of salicylaldimine ligands substantially increase polymerization activity. While these ligands afford highly active catalysts, their syntheses require multistep procedures with very low yields. Our particular interest in the design of novel Ni salicylaldiminato complexes stems from the recent finding that the known isopropyl-substituted complexes enable the synthesis of latexes of high-molecular-weight polyethylene, which are, to date, inaccessible by other techniques. Such polyolefin latexes can provide environmentally friendly and economically attractive coatings, which, for example, can be stable towards UV light and hydrolysis at the same time in contrast to current commodity coatings. In view of applications, a very active catalyst based on conveniently accessible ligands, and that is suited to polymerization in emulsion to higher-molecular-weight polyethylene is a prerequisite. Such a system is equally attractive for fundamental studies of catalytic polymerization in emulsion, in which well-defined catalyst precursors are also desirable. Our investigations subject to this report were initiated by the reasoning that an aryl substituent with strongly electron-withdrawing groups could provide steric bulk and electron withdrawing properties at the same time. Suzuki coupling provided a convenient synthetic method for the introduction of electron-withdrawing substituted aryl groups in the C2 and C6 position of the aniline aryl ring (Scheme 1). A series of salicylaldimine ligands with systematically varied electronic properties, 1a–e, resulted from the condensation of the corresponding substituted anilines with 3,5-diiodo-salicylaldehyde. The C NMR resonances of the compounds were fully assigned by H–H COSY, heteronuclear H-C 2D NMR and H–C 2D longrange-coupling NMR spectroscopy. The chemical shifts of the carbon atom para to the imine function in 1a–e (atom labeled p in Scheme 1) are d= 126.90, 126.96, 126.55, 126.48, and 126.56 ppm, respectively, and for the imine carbon atom, C= N, d= 168.42, 168.05, 166.99, 166.23, and 166.26 ppm were observed. Although the differences in chemical shifts are moderate, this trend follows the electron withdrawing/donating character of the R group and indicates that the electronic character of the substituents R in 1 indeed affects the electronic properties of the neighboring aryl ring and the imine function. Reaction of 1a–e in diethylether with [(tmeda)Ni(CH3)2] [12] (tmeda=N,N,N’,N’-tetramethylethylenediamine) in the presence of excess pyridine afforded the neutral methylnickel(ii) complexes 2a–e in high yield (Scheme 1). The molecular structure of 2a and 2c was determined by single-crystal X-ray crystallography (Figure 1). 14] To our knowledge, these are the first examples of structurally characterized neutral methylnickel complexes, which are precursors to very active olefin polymerization catalysts. Such methyl complexes are of particular interest, in comparison to the more frequent phenyl complexes [*] Dr. M. A. Zuideveld, Dipl. Chem. P. Wehrmann, Priv.-Doz. Dr. S. Mecking Institut f$r Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universit*t Freiburg Stefan-Meier-Strasse 31, 79104 Freiburg (Germany) Fax: (+49)761-203-6319 E-mail: stefan.mecking@makro.uni-freiburg.de

Remote Substituents Controlling Catalytic Polymerization by Very Active and Robust Neutral Nickel(II) Complexes

More than 70 million tons of polyethylene and polypropylene are produced annually. The majority is prepared by catalytic polymerization employing Ziegler or Phillips catalysts based on early transition metals. More recently, olefin polymerization by complexes of late transition metals has also received increasing attention. A major motivation is their higher tolerance towards polar reagents due to a reduced oxophilicity by comparison to early transition-metal catalysts. Thus, ethylene and 1-olefins can be copolymerized with acrylates in a random fashion, and ethylene homoand copolymerizations can be carried out in aqueous emulsion to afford polymer latexes (i.e., aqueous dispersions of polymer particles of about 50–1000 nm size). The discovery by Brookhart and co-workers of the unique catalytic properties of cationic nickel and palladium diimine catalysts in olefin polymerization has given a strong impulse to the field. As a result, polymerization with neutral Ni complexes has received renewed interest, as these catalysts are expected to be more functional-group tolerant than their cationic Ni counterparts. However, catalyst activity and stability over time and the capability to form polymers with higher molecular weights at the same time are critical issues, particularly if the effort for catalyst synthesis is also considered. By analogy with the influence of bulky alkyl or aryl groups in cationic diimine complexes, in neutral Ni kN,O salicylaldiminato complexes bulky isopropyl groups on theN-aryl moiety retard chain transfer, which is supported by computational studies by Ziegler and co-workers. Introduction of electron-withdrawing substituents in the ortho or para position of the O donor in neutral nickel(ii) complexes has been reported to increase catalytic activities substantially, again in accordance with theoretical calculations. Most specifically for this class of catalysts, Grubbs and co-workers have shown that bulky groups in the C3 position of the Ocoordinating phenolate moiety of salicylaldimine ligands substantially increase polymerization activity. While these ligands afford highly active catalysts, their syntheses require multistep procedures with very low yields. Our particular interest in the design of novel Ni salicylaldiminato complexes stems from the recent finding that the known isopropyl-substituted complexes enable the synthesis of latexes of high-molecular-weight polyethylene, which are, to date, inaccessible by other techniques. Such polyolefin latexes can provide environmentally friendly and economically attractive coatings, which, for example, can be stable towards UV light and hydrolysis at the same time in contrast to current commodity coatings. In view of applications, a very active catalyst based on conveniently accessible ligands, and that is suited to polymerization in emulsion to higher-molecular-weight polyethylene is a prerequisite. Such a system is equally attractive for fundamental studies of catalytic polymerization in emulsion, in which well-defined catalyst precursors are also desirable. Our investigations subject to this report were initiated by the reasoning that an aryl substituent with strongly electron-withdrawing groups could provide steric bulk and electron withdrawing properties at the same time. Suzuki coupling provided a convenient synthetic method for the introduction of electron-withdrawing substituted aryl groups in the C2 and C6 position of the aniline aryl ring (Scheme 1). A series of salicylaldimine ligands with systematically varied electronic properties, 1a–e, resulted from the condensation of the corresponding substituted anilines with 3,5-diiodo-salicylaldehyde. The C NMR resonances of the compounds were fully assigned by H–H COSY, heteronuclear H-C 2D NMR and H–C 2D longrange-coupling NMR spectroscopy. The chemical shifts of the carbon atom para to the imine function in 1a–e (atom labeled p in Scheme 1) are d= 126.90, 126.96, 126.55, 126.48, and 126.56 ppm, respectively, and for the imine carbon atom, C= N, d= 168.42, 168.05, 166.99, 166.23, and 166.26 ppm were observed. Although the differences in chemical shifts are moderate, this trend follows the electron withdrawing/donating character of the R group and indicates that the electronic character of the substituents R in 1 indeed affects the electronic properties of the neighboring aryl ring and the imine function. Reaction of 1a–e in diethylether with [(tmeda)Ni(CH3)2] [12] (tmeda=N,N,N’,N’-tetramethylethylenediamine) in the presence of excess pyridine afforded the neutral methylnickel(ii) complexes 2a–e in high yield (Scheme 1). The molecular structure of 2a and 2c was determined by single-crystal X-ray crystallography (Figure 1). 14] To our knowledge, these are the first examples of structurally characterized neutral methylnickel complexes, which are precursors to very active olefin polymerization catalysts. Such methyl complexes are of particular interest, in comparison to the more frequent phenyl complexes [*] Dr. M. A. Zuideveld, Dipl. Chem. P. Wehrmann, Priv.-Doz. Dr. S. Mecking Institut f$r Makromolekulare Chemie und Freiburger Materialforschungszentrum der Albert-Ludwigs-Universit*t Freiburg Stefan-Meier-Strasse 31, 79104 Freiburg (Germany) Fax: (+49)761-203-6319 E-mail: stefan.mecking@makro.uni-freiburg.de