327,331 research outputs found
Metal complexes as potential ligands : the deprotonation of aminephenolate metal complexes
No full textThe cationic nickel, copper and zinc complexes of tris-(2-hydroxybenzyl)-aminoethylamine (H6TrenSal) have been deprotonated using potassium hydroxide. The nickel complex can be sequentially deprotonated to form a series of compounds namely, [(H6TrenSal)Ni]+, [(H6TrenSal)Ni] and "[(H6TrenSal)Ni]K". The latter is isolated as a mixture of species namely [{(H6TrenSal)Ni}K(EtOH)]2, [{(H6TrenSal)Ni}K(EtOH)2-μ-OH2]2 and [{(H6TrenSal)Ni}K(EtOH)2-μ-EtOH]2, which co-crystallise in a roughly 50:27.5:22.5 ratio. In contrast the deprotonation of [(H6TrenSal)M]+ (M = Cu, Zn) results in the formation of tetrameric complexes [({(H6TrenSal)Ni}K(OH2)2)4(μ4-OH2)]
[(VIVO)2MII5] (M = Ni, Co) Anderson Wheels
No full textHeterometallic Anderson wheels of formula [(VIVO)2MII5(hmp)10Cl2](ClO4)2·2MeOH (M = Ni, 1; Co, 2) have been synthesised from the solvothermal reaction of M(ClO4)2·6H2O and VCl3 with hmpH (2-(hydroxymethyl)pyridine). The metallic skeleton describes a centred hexagon, with the two vanadyl ions sitting on opposing sides of the outer ring. Magnetic susceptibility and magnetisation measurements indicate the presence of both ferromagnetic and antiferromagnetic exchange interactions. Theoretical calculations based on density functional methods reproduce both the sign and strength of the exchange interactions found experimentally, and rationalise the parameters extracted
Electron Microscopy Characterization of Ni-Cr-B-Si-C Laser Deposited Coatings
No full textDuring laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.
Desenvolvimentos de estruturas muitiferroicas de filmes finos de ligas Ni-Mn-Ga e PMN-PT
No full textMestrado em Ciência e Engenharia de MateriaisLigas de forma ferromagnética em sistemas Ni-Mn-Ga são uma classe recente de
materiais activos que podem gerar deformações de até 10% induzidas por um campo
magnético por um rearranjo de maclas. Esta e outras propriedades físicas destas ligas
têm importância tecnológica. Este trabalho investiga as propriedades de filmes finos
de ligas de Ni-Mn-Ga sobre diferentes substratos, incluindo substratos activos
(piezeléctricos). Para estudar as propriedades de filmes finos da liga, heteroestruturas
sob a forma de Ni-Mn-Ga/substrato foram produzidas por RF sputtering com
magnetrão utilizando temperaturas de deposição de 3200C, 3700C, 4000C sobre
substratos de Al2O3, MgO, SrTiO3 e PMN-PT. A influência da temperatura do
substrato durante a deposição nas propriedades estruturais e magnéticas de filmes finos
foi estudada. Além disso, o acoplamento magnetoeléctrico entre Ni-Mn-Ga como filme
fino material ferromagnético e PMN-PT como material piezoeléctrico foi investigada.
O efeito magnetoeléctrico foi investigado apenas em filmes depositados a temperatura
do substrato de 3700C e 4000C. As propriedades estruturais foram estudadas por
difração de raios-X, as propriedades magnéticas foram investigadas por VSM, SQUID,
e MFM, e o efeito magnetoeléctrico foi estudado por técnica lock-in. A medida
estrutural mostrou que os filmes depositados são parcialmente cristalinos e o grau de
cristalinidade aumenta como o aumento da temperatura do substrato. Fases austenita e
martensita foram observadas nesses filmes. Os resultados da medição magnética
mostram que todos os filmes depositados exibem comportamento ferromagnético e o
comportamento ferromagnético é favorecido com o aumento da temperatura do
substrato. Todos os filmes depositados na temperatura do substrato de 400ºC
apresentam temperaturas dev Curie acima da temperatura ambiente: 337K para Ni-Mn-
Ga/PMN-PT, 345K para Ni-Mn-Ga/STO e 348K para Ni-Mn-Ga/Al2O3. Nenhuma
evidência separada de temperatura de transição estrutural foi observada para nos
filmes. Os resultados das medições magnetoeléctricas mostram que as heteroestruturas
multiferróicas Ni-Mn-Ga/PMN-PT apresentam efeito magnetoelétrico. O valor
máximo medido para a tensão magnetoeléctrica induzida para filmes depositados à
temperatura do substrato de 3700C e 4000C são 3.16mV/cmOe e 3.02mV/cmOe,
respectivamente.Ferromagnetic shape memory alloys (FSMAs) in Ni-Mn-Ga systems are a
recent class of active materials that can generate large magnetic field induced
strains up to 10% by twin rearrangement. This and other physical properties
these alloys have many technological importance. This work investigates the
properties of Ni-Mn-Ga alloy thin films on different substrates including active
substrate (piezoelectric). To study the properties of thin films of the alloy, the
heterostructures in the form of Ni-Mn-Ga/substrate were produced by RF
magnetron deposition system using substrate deposition temperatures of
3200C, 3700C, and 4000C, where the substrates used were Al2O3, MgO, SrTiO3
and PMN-PT. The influences of deposition substrate temperature on structural
and magnetic properties of sputtered thin films on the aforementioned
substrates were studied. Moreover, magnetoelectric coupling between Ni-Mn-
Ga thin film as ferromagnetic material and PMN-PT as piezoelectric material
was investigated. The magnetoelectric effect was investigated only on films
deposited at substrate temperature of 3700C and 4000C. The structural
properties were studied by x-ray diffraction, magnetic properties were
investigated by VSM, SQUID, and MFM, and the magnetoelectric effect was
studied by lock-in technique. The structural measurement has shown that asdeposited
films are partially crystalline and degree of crystallinity increases as
substrate temperature increase. Austenite and martensite phases have been
observed in these films. The magnetic measurement results show that all films
as-deposited display ferromagnetic behaviour and ferromagnetic behaviour
improvements are observed as substrate temperature increases. All films
deposited at substrate temperature of 4000C exhibit Curie temperatures above
room temperature which are 337K for Ni-Mn-Ga/PMN-PT, 345K for Ni-Mn-
Ga/STO, 348K for Ni-Mn-Ga/Al2O3. No separate signature of structural
transition temperature was observed for all these films. The magnetoelectric
measurement results show that a heterostructure of Ni-Mn-Ga/PMN-PT
multiferroic exhibit magnetoelectric effect. The measured maximum induced
magnetoelectric voltage for films deposited at substrate temperature of 3700C
and 4000C are 3.16mV/cmOe and 3.02mV/cmOe, respectively
Investigation into the dehydration of selenate doped Na 2 M(SO 4 ) 2 ·2H 2 O (M = Mn, Fe, Co and Ni): Stabilisation of the high Na content alluaudite phases Na 3 M 1.5 (SO 4 ) 3-1.5x (SeO 4 ) 1.5x (M = Mn, Co and Ni) through selenate incorporation
No full textIn this paper we report an investigation into the phases formed on dehydration of Na2M(SO4)2−x(SeO4)x·2H2O (0 ≤ x ≤ 1; M = Mn, Fe, Co and Ni). For the Fe series, all attempts to dehydrate the samples doped with selenate resulted in amorphous products, and it is suspected that a side redox reaction involving the Fe and selenate may be occurring leading to phase decomposition and hence the lack of a crystalline product on dehydration. For M = Mn, Co, Ni, the structure observed was shown to depend upon the transition metal cation and level of selenate doping. An alluaudite phase, Na3M1.5(SO4)3-1.5x(SeO4)1.5x, was observed for the selenate doped compositions, with this phase forming as a single phase for x ≥ 0.5 M = Co, and x = 1.0 M = Ni. For M = Mn, the alluaudite structure is obtained across the series, albeit with small impurities for lower selenate content samples. Although the alluaudite-type phases Na2+2y(Mn/Co)2−y(SO4)3 have recently been reported [1,2], doping with selenate appears to increase the maximum sodium content within the structure. Moreover, the selenate doped Ni based samples reported here are the first examples of a Ni sulfate/selenate containing system exhibiting the alluaudite structure
Role of structural defects in olivine cathodes
No full textThe high rate capability and structural stability of the olivine phosphates attracted a lot of interest as promising cathode materials for high energy density batteries. Alteration on these cathode materials, for instance, reducing particle size, conductive coating and metal ion doping were performed in order to improve the conductivity and to obtain high specific capacity. Wide range of transition metal ions with range of valences (M 1+ to M 5+) was successfully doped both in M 1 site (Li) and M 2 site (M) of olivine LiMPO 4 (M = Fe, Mn, Co and Ni) cathode. The large charge difference between the doped supervalent ions and M cations at the M 2 site, limited the use of supervalent cations in the olivines. However, the supervalent dopants (namely; Cr 3+, Ti 4+, Nb 5+) are reported to be successfully substituted in the olivine with an improvement in electrical and ionic conductivity. The amount of defect can be reduced by low concentration of dopants, choosing suitable synthesis method and optimized reaction conditions. Charge compensation vacancies accomplished through aliovalent doping reduces the grain size and widens the Li + migration path resulting in faster Li + diffusion. However, the drastic improvement in electrical conductivity for the aliovalent doping is still unclear. Rather writing a lengthy standard review, this manuscript intends to describe briefly the lattice defects owing to metal ion doping and its influence in improving the cathode performance of the olivine phosphates. This gives a new approach in this field
Electrodeposition of Ni-Si Schottky barriers
No full textElectrodeposition is being used to fabricate magnetic microstructures directly on patterned n-type Si wafers of various substrate resistivities. The Ni-Si Schottky barrier is characterized and found to be of high quality for relatively low Si resistivities (1-2 Omega(.)cm), with extremely low reverse leakage. It is shown that a direct correlation exists among the electrodeposition potential, the roughness, and the coercivity of the films. A conductive seed layer or a back contact is not compulsory for electrodeposition on Si with resistivities up to 15 Omega(.)cm. This shows that electrodeposition of magnetic materials on Si might be a viable fabrication technique for magnetoresistance and spintronics applications
The magnetocaloric effect of Gd-Tb-Dy-Al-M (M = Fe, Co and Ni) high-entropy bulk metallic glasses
No full textIn this article, we report the formation of the high-entropy Gd20Tb20Dy20Al20M20 (M = Fe, Co and Ni) bulk metallic glasses with good magnetocaloric properties. Compared with most of the rare earth based metallic glasses, these alloys are found to have the comparably large maximum magnetic entropy changes (Delta S-M), but much broader widths of the Delta S-M peaks, and hence larger refrigerant capacity (RC). This can be attributed to the combination of the spin glass behaviors and the complicated compositions in these alloys. Our work show that the high entropy bulk metallic glasses is a promising candidate material as the magnetic refrigerant. (C) 2014 Elsevier Ltd. All rights reserved
Preparation and temperature cycling reliability of electroless Ni(P) under bump metallization
No full textThe reliability of electroless Ni(P) under-bump metallization (UBM) was evaluated via temperature cycling and solder bump shear strength tests. Commercial diodes and dummy dies fabricated in-house were used as substrates for the electroless Ni(P) UBM deposition. Solder bumps were formed after reflowing eutectic 63Sn37Pb solder foils over the Ni(P) UBM. The solder bump shear strength was measured before and after different temperature cycling. The results from this study showed that the UBM thickness and dimension had important effects on the solder bump shear strength and reliability. Both the larger UBM dimension and larger UBM thickness tended to induce higher stress in the UBM, which resulted in the lower solder bump shear strength and lower temperature cycling reliability. A better UBM structure solution for high current electronic packaging application is indicated in this pape
Effects of the alloy composition on phase constitution and properties of laser deposited Ni-Cr-B-Si coatings
No full textThree Ni-Cr-B-Si hardfacing alloy powders with different Cr contents and Si to B ratios were deposited at cladding speeds of 5-40 mm/s on steel substrate using laser beam and the alloy composition-phase formation-properties relationships in the deposits were studied using several experimental techniques. Two general groups of compositions could be defined in this alloy system; the high-alloy grades characterized by numerous Cr boride precipitates, a low Si/B ratio and substantial Ni-B-Si eutectics, and the low-alloy grades with very little Cr boride precipitates, a high Si/B ratio and limited amounts of interdendritic eutectics. The findings confirmed that phase formation of Ni-Cr-B-Si laser deposited coatings primarily depends on the Cr content and Si/B ratio with the former controlling the amount of Cr-rich precipitates and the latter influencing the nature of the eutectic structures. In addition, it is shown that both Cr-rich precipitates and eutectic structures contribute to the functional properties of the coatings such as hardness and cracking susceptibility. The correlation between phase constitutions produced by different compositions and the hardness/cracking tendency is established and discussed.
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