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Multistep Heat-Treatment Effects on Electrospun Nd-Fe-B-O Nanofibers

Jeon E. J., Eom N. S. A., Lee J., Lee B., Cho H. M., On J. S., Choa Y.-H, Kim B. S.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1433--1437

EN

Neodymium-Iron-Boron (Nd-Fe-B) magnets are considered to have the highest energy density, and their applications include electric motors, generators, hard disc drives, and MRI. It is well known that a fiber structure with a high aspect ratio and the large specific surface area has the potential to overcome the limitations, such as inhomogeneous structures and the difficulty in alignment of easy axis, associated with such magnets obtained by conventional methods. I n this work, a suitable heat-treatment procedure based on single-step and multistep treatments to synthesize sound electrospun Nd-Fe-B-O nanofibers of Φ572 nm was investigated. The single-step heat-treated (directly heat-treated at 800°C for 2 h in air) samples disintegrated along with the residual organic compounds, whereas the multistep heat-treated (sequential three-step heat-treated including three steps;: dehydration (250°C for 30 min in an inert atmosphere), debinding (650°C for 30 min in air), and calcination (800°C for 1 h in air)) fibers maintained sound fibrous morphology without any organic impurities. They could maintain such fibrous morphologies during the dehydration and debinding steps because of the relatively low internal pressures of water vapor and polymer, respectively. In addition, the NdFeO3 alloying phase was dominant in the multistep heat-treated fibers due to the removal of barriers to mass transfer in the interparticles.

2

Microstructure Development of Spark Plasma Sintered Ti-Nb Alloy by Heat Treatment

Haq M. A., Abbas S. F., Eom N. S. A., Kim T. S., Lee B., Park K.-T., Kim B. S.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1429--1432

EN

The β-phase Titanium (β-Ti) alloys have been under the spotlight in the recent past for their use as biomedical prosthetic materials owing to their excellent properties such as low elastic modulus, high corrosion resistance and tensile strength. Recently, Niobium (Nb) has gained a lot of attention as a β-phase stabilizing element in Ti alloys to replace Vanadium (V) due to its excellent solubility in Ti, low elastic modulus and biocompatibility. In this work, low cost Ti-20Nb binary alloy has been fabricated via powder metallurgy procedures. The blended powder mixtures of Ti and Nb were sintered at 900°C for 20 mins by the Spark Plasma Sintering (SPS) with an applied uniaxial pressure of 40 MPa. The heating rate was fixed at 50°C/min. The sintered alloy was subject to heat treatments at 1200°C in vacuum condition for various time durations. The characterizations of microstructure obtained during this process were done using FE-SEM, EDS and XRD. By increasing heat treatment time, as understood, the volume of residual Nb particles was decreased resulting in accelerated diffusion of Nb into Ti. Micro hardness of the alloy increased from 340 to 355 HV with the increase in β phase content from 30 to 45%. The resultant alloys had relatively high densities and homogenized microstructures of dispersed lamellar β grains in α matrix.

3

Fabrication and Characterization of CoCrFeNiMn High Entropy Alloy Powder Processed by Gas Atomization

Park T. G., Lee S. H., Lee B., Cho H. M., Choi W. J., Kim B. S., Shin K. S., Kim T.-S.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

1055--1059

EN

In this study, precisely controlled large scale gas atomization process was applied to produce spherical and uniform shaped high entropy alloy powder. The gas atomization process was carried out to fabricate CoCrFeNiMn alloy, which was studied for high ductility and mechanical properties at low temperatures. It was confirmed that the mass scale, single phase, equiatomic, and high purity spherical high entropy alloy powder was produced by gas atomization process. The powder was sintered by spark plasma sintering process with various sintering conditions, and mechanical properties were characterized. Through this research, we have developed a mass production process of high quality and spherical high entropy alloy powder, and it is expected to expand applications of this high entropy alloy into fields such as powder injection molding and 3D printing for complex shaped components.

4

A study of accountability in work-based learning: The Learning Representative Initiative in the UK

Lee B., Cassel C.

Management

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2004

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Vol. 8, no 1

171-181

EN

Stimulating the lifelong learning of a workforce is an important Human Resource Management issue, while ensuring that management provide such stimulation is an important accountability issue for employees' representatives. The United Kingdom's Employment Act (2002) granted trade union learning representatives' statutory rights to paid time off to diagnose workers' learning needs and to negotiate their learning. One way of exploring whether employers are providing learning opportunities and are accountable to trade unions for such learning is by examining whether trade union websites commend best practice of any companies. The purpose of this paper is to report an example from a trade union website of best practices of learning negotiated between an employer and a trade union, as a consequence of the initiative. The discussion is set in a context of the benefits of learning and an account of the extent to which trade union members in different occupations have enjoyed learning in the past and stand to benefit from the union learning representative initiative. The case is used to highlight some of the steps that were taken to ensure the initiative was successful. The discussion concludes by considering the broader lessons of the union learning representative initiative.

5

After the doc.com bubble has burst: UK Venture Capitalists, short-term accounting criteria and investment in start-up companies

Alao S., Lee B.

Management

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2003

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Vol. 7, no 1

111-122

EN

This paper reports findings from a questionnaire survey that sought to establish whether venture capitalists were using inappropriate, short-term accounting criteria to assess and monitor investment in start-up, internet companies. It found that while venture capitalists used some short-term criteria, these may be appropriate in the wake of many internet companies' bankruptcy before ever paying dividends.

6

Inventory management, economic order quantity, economic batch size, just-in-time and strategy

Lee B., Bowhill B.

Management

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2002

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Vol. 6, no 1

155-166

EN

This article examines the relationship between a company's inventory policies and their broader strategic objectives. Rather than accepting that one fonn of inventory policy - such as Just-in- Time - is universally superior and so should feature in every company's strategy, the article uses fonnulaic definitions of different inventory policies to investigate inventory arrangements at a case study company. The article concludes by calling for an analysis of actual inventory requirement and arrangements prior to finalising strategy.