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Joseph Durk

In July 2015 I graduated from Aberystwyth University with a First Class BSc(Hons) degree in Physics. Over the course of my final undergraduate year I was introduced to the Diamond Science & Technology CDT via a friend studying the MSc course at the University of Warwick. With an interest in condensed matter physics the content of the course appealed to me greatly, and so I approached Professor Andy Evans about the potential of a PhD. I am extremely excited to begin training the specific skills required for the successful completion of my work on cubic boron nitride behaviour, as well as gaining knowledge on diamond and the industry at large. As a multi-disciplinary course I understand that some aspects will be tricky, but look forward to meeting and learning from international experts in the various fields, and doing so with a like-minded cohort.


PhD Title: Spectroscopy studies of Polycrystalline Cubic Boron Nitride Materials (cBN) to build Behaviour Models in selected Precision Machining Applications
PhD Supervisor: Prof. Andrew Evans
Institution: Aberystwyth University

The project undertaken focuses on a face-centred cubic crystal known as cubic boron nitride (cBN), analogous to diamond in many ways. Similarities in structure and bonding relate to a similar exhibition of extreme material properties, in particular cBN is often considered second only to diamond on the Knoop hardness scale. [1] Polycrystalline cubic boron nitride (PcBN) is the broad term for compacts formed of cBN crystals locked within a metallic and/or ceramic 'binder' material. These compacts are utilised widely in the tooling industry for the mould machining of ferrous metal work-pieces, particularly hardened steels and other iron and nickel-containing alloys. [2] At the interface of the tool and the metal being worked, temperatures can reach upwards of 1100 K, which is believed to be a large contributing factor in observed chemical degradation of the tool tips over time. However, direct observation of the interface is often impractical during normal operation, and so typically surface studies are limited to before/after comparisons. [3]

The aim of the project is to characterise interactions between the main constituents of these alloys and the PcBN compacts in real time, within a controlled ultra-high vacuum environment. To achieve this, real-time x-ray photoelectron spectroscopy (XPS) with a coupled Raman spectroscopy system is utilised in conjunction with a sample heating stage, to observe cBN and PcBN surfaces as they reach temperatures expected during industrial operation. Further, thin nanometre films of iron are deposited onto the compact surface such that electrons from the PcBN substrate are still observable at the analyser. This allows for real-time study of the chemical and structural alterations relating to the compact as a result of high temperature and the Fe interface.

By understanding temperature regimes relating to activation energies of the PcBN and work-piece at the surface, it is hoped that the knowledge can be applied to the formation of more durable compacts, less susceptible to chemical wear. This can lead to more efficient throughput in sectors where these ferrous alloys are vital, particularly in aerospace and automotive applications.

Work is carried out with collaboration from industrial sponsors, Element Six.

References

[1] S. N. Monteiro, A. L. D. Skury, M. G. De Azevedo, and G. S. Bobrovnitchii, “Cubic boron nitride competing with diamond as a superhard engineering material - An overview,” J. Mater. Res. Technol., vol. 2, no. 1, pp. 68–74, 2013.

[2] M. W. Cook and P. K. Bossom, “Trends and recent developments in the material manufacture and cutting tool application of polycrystalline diamond and polycrystalline cubic boron nitride,” Int. J. Refract. Met. Hard Mater., vol. 18, no. 2, pp. 147–152, 2000.

[3] R. T. Coelho, E. G. Ng, and M. A. Elbestawi, “Tool wear when turning hardened AISI 4340 with coated PCBN tools using finishing cutting conditions,” Int. J. Mach. Tools Manuf., vol. 47, no. 2, pp. 263–272, 2007.


Teaching

Teaching modules include Classical Dynamics, and Introduction to Computational and Experimental Physics. Responsibilities for the former include regular tutorial sessions, working through problem sheets that accompany lecture notes. The latter includes demonstrating both within a standard undergraduate physical laboratory, and a Python computing workshop setting.


Prizes

July 2017 - Awarded best First Year Report for postgraduate students within the Institute of Mathematics, Physics and Computer Science at Aberystwyth University.


Conferences

De Beers 68th Diamond Conference, The University of Warwick. Poster Presentation "Temperature-induced changes in cubic boron nitride surface chemistry." July 2017

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Joseph Durk

Aberystwyth University

Department of Physics, IMPACS
Room 1.44, The Physical Sciences Building
Aberystwyth, SY23 3FL

Website

Tel: 01970 62 8536

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