• Journal of Microbiology and Biotechnology
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• v.18 no.6
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• pp.1040-1043
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• 2008

Klebsiella oxytoca CCUG 15788 is resistant to $Ni^{2+}$ at a concentration of 10 mM and grows in an inducible manner when exposed to lower concentrations of $Ni^{2+}$. The complete genomic sequence of a 4.2-kb HindIII-digested fragment of this strain was determined from genomic DNA. It was shown to contain four nickel resistance genes (nirA, nirB, nirC, and nirD) encoding transporter and transmembrane proteins for nickel resistance. When the plasmid pKOHI4, encoding nirABCD, was transformed into Escherichia coli JM109, the cells were able to grow in Tris-buffered mineral medium containing 3 mM nickel. TnphoA'-1 insertion mutants in the four nickel genes nirA, nirB, nirC, and nirD showed nickel sensitivity. The nir genes were heterogeneously expressed in E. coli, suggesting functional roles of these genes in nickel resistance.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.114-120
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• 2002

A 1,989-bp genomic region encoding nickel resistance genes was isolated from Legionella pneumophila, a pathogen for legionellosis. From a sequencing and computer analysis, the region was found to harbor two structural genes, a nreB-like protein gene (1,149 bp) and a nreA-like protein gene (270 bp), in a row. Both genes exhibited a significant degree of similarity to the corresponding genes from Synechocystis sp. PCC6803 ($54\%$ amino acid sequence identity) and Achromobacter xylosoxidans 31A ($76\%$). The gene was successfully expressed in E. coli MG1655 and conferred a nickel resistance of up to 5 mM in an LB medium and 3 mM in a TMS medium including gluconate as the sole carbon source. E. coli harboring the nickel resistance gene also exhibited a substantial resistance to cobalt, yet no resistance to cadmium or zinc. Since the extracellular concentration of nickel remained constant during the whole period of cultivation, it was confirmed that the nickel resistance was provided by an efflux system like the $Ni^2＋$permease (nrsD) of Synechocystis sp. strain PCC6803. Since polyphosphate (poly-P) is known as a global regulator for gene expression as well as a potential virulence factor in E. coli, the nickel resistance of a ppk mutant of E. coli MG 1655 harboring the nickel resistance gene from L. pneumophila was compared with that of its parental strain. The nickel resistance was significantly attenuated by ppk inactivation, which was more pronounced in an LB medium than in a TMS medium.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.478-483
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• 2011

Cast mold has low wear-resistance comparing with other alloyed molds which result in lower production rate and high cost of products. Recently, various weld methods are being applied to increase the wear-resistance of molds and to extend mold life. Among them, nickel alloy weld process increases the hardness irrelevant to its machinability and creates very uniform structures. In addition, it causes better wear-resistance and reduces shrinkage defects. In this paper, we analyze the mold surface cracks welded by nickel alloy and propose the methods to improve the mold surface and its wear-resistance. It has been found that nickel alloy weld does not affect the inside crack of mold but has an influence on the surface crack seriously. Results show that the start and growth of fatigue cracks have been delayed about 3 times and reduced approximately 75%, respectively, and the mold surface cracks are decreased about 5.7 times.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.73-80
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• 1989

Preparation and characteristics of electroless Ni-P and Ni-B systems for semiconducting ceramics have been investigated as a function of deposit rate, reducing agent and pH variation. The effect of DMAB as ruducing agent is greater than that of sodium hypophosphite. The nickel electrode prepared from the nickel-phosphorus system with sodium hypophosphite shows low contact resistance of 0.99ohm compared with the resistance of 10chm in the electrode prepared from the nickel-boron system with DMAB. The contact resistance increases with increasing pH valuein the nickel-phosphorus system with sodium hypophosphite. The ratio of Ni to P is about 76.0/24.0 for the contact resistance of 0.99ohm in the above system.

• Journal of the Korean institute of surface engineering
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• v.25 no.3
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• pp.107-116
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• 1992

The optimum thickness of Pd-Ni plated layers used as an electrical contact film was investigated by evaluating mechanical, thermal and environmental characteristics. The variations of morphologies and chemical compositions were studied by using SEM, EDS and ESCA. As a result of wear test, the wear resistance behavior of the gold plated layers was not changed with the sliding velocity changes. The palladium-nickel plated layer showed better wear resistance than the gold plated layer at low sliding velocity, but it showed poor wear resistance at high sliding velocity. Under the thermal condition of $400^{\circ}C$ in air, the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze formed copper oxide on the surface layer by rapid diffusion of copper whereas the gold thickness of $0.8\mu\textrm{m}$ deposited on nickel and palladium-nickel underplate was stable at $400^{\circ}C$. Under the sulfur dioxide environments, the gold thickness of $0.3\mu\textrm{m}$ deposited on the nickel thickness of$ 3\mu\textrm{m}$ and the palladium-nickel thickness of $2\mu\textrm{m}$ underplate was more corrosion-resistant than the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze. Under the nitric acid vapor environment, corrosion resistance of the gold film was superior to an equivalent thickness of the palladium-nickel film.

• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.26-35
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• 1996

The Ni-SiC composite plating was performed in a Watt nickel solution and the wear resistance of the composite layer was studied on a pin-on-flat type wear tester. The volume losses and friction coefficients were measured. It was found that the quantity of SiC powder in the composite layers was affected by SiC concentration, pH, temperature, and agitation speed in the Watt nickel solution. The hardness and wear resistance of the coatings increased with SiC content. The quantity of SiC powder in the coating from a nickel sulfamate solution is larger than that of the Watt nickel solution, because the amount of nickel ions absorbed on the SiC powder in the nickel sulfamate solution is greater than that in the Watt's solution.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.196-199
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• 2000

Electroless plating is the desirable surface treatment method which is being widely used to all kinds of material such as requiring corrosion resistance, wear resistance and conductivity, especially plating of nonconductive material. Electroless nickel deposit has particular characteristics including non-magnetic property, amorphous structure, wear resistance, corrosion protection and thermal stability. In this study, electroless nickel plating was studied with an change in hardness and corrosion resistance of electroless nickel-phosphorus deposit depending on heat treatment. The highest hardness value was obtained by heat treatment at $500^{\circ}C$ Corrosion resistance of deposit, which had been heated at $300^{\circ}C$, was excellent when it was immersed in 1M $H_2SO_4$ solution for 60 hrs.

• Journal of the Korean institute of surface engineering
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• v.46 no.6
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• pp.235-241
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• 2013

In this study, the effects of alloying elements and thermal aging on the contact resistance of electroplated gold alloy layers were investigated by surface analysis using X-ray photoelectron spectroscopy (XPS). The contact resistance of Au-Ag alloy was lower than that of Au-Ni or Au-Co alloy after thermal aging. The XPS results show that nickel and oxygen present as nickel oxides such as NiO and $Ni_2O_3$ on the surface of gold layers after thermal aging. The increase in the contact resistance after thermal aging is attributable to the nickel oxide layer formed on the surface of the gold layers. The content of nickel diffused from the underlayer during the thermal aging was high in the order of Au-Co, Au-Ni and Au-Ag alloy because the area of grain boundary was large in the order of Au-Ag, Au-Ni and Au-Co alloy.

• Journal of the Korean institute of surface engineering
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• v.19 no.3
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• pp.83-91
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• 1986

Codeposited of boron nitride(BN) particle dispersed into electroless nickel-phosphours (Ni-P) and nickel-boron(Ni-B) platings were studied for the purpose of developing the wear resistance and lubricity. BN can be codeposited from electroless nickel plating bath with $NaH_2PO_2$ and $NaBH_4$ as the reducing agents. Most dispersolids were distributed uniformly in the Ni-P and Ni-B matrix. Abrasion loss decreased with increasing amount of codeposits and reached a constant value 2.4 percent by volume percent of BN particle. The wear resistance and the friction coefficient of the heat treated BN composite coatings were improved about three times than that of as-coatings. The BN composite coatings were more wear resistance than hard chromium. Ni-B-BN composite coatings showed lower wear resistance and friction coefficient than Ni-P-BN. The BN content of the deposite was found to be 2.4 v/o for these optium conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.5
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• pp.536-541
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• 2015

Copper has been used extensively as an electric wire or as a base material in various types of machineries owing to its good electrical and thermal conductivity and good fabricating property, as well as its good corrosion resistance compared to iron. Furthermore, the copper-nickel alloy has significant corrosion resistance in severely corrosive environments. Although, cupro-nickel alloy shows better corrosion resistance than the brass and bronze series, this alloy also corroded in severely corrosive environments, including aggressive chloride ions, dissolved oxygen, and condition of fast flowing seawater. In this study, and annealing treatment at various annealing temperatures was carried out on the cupro-nickel (Cu-10%Ni) alloy, and the effects of annealing were investigated using electrochemical methods, such as measuring the polarization and impedance behaviors under flowing seawater conditions. The corrosion resistance increased by annealing compared to non heat treatment in the absence of flowing seawater. In particular, the sample annealed at $200^{\circ}C$ exhibited the best corrosion resistance. The impedance in the presence of flowing seawater showed higher values than in the absence of flowing seawater. Furthermore, the highest impedances was observed in the sample annealed at $800^{\circ}C$, irrespective of the present of flowing seawater. Consequently, the corrosion resistance of cupro-nickel (Cu-10%Ni) alloy in a severely corrosive environment can be improved somewhat by annealing.