Capital investment in an Instrument to Measure Particle Size Distribution (PSD)
Lead Research Organisation:
University of Huddersfield
Department Name: Sch of Computing and Engineering
Abstract
We propose to procure a specialised instrument for measuring particle size distribution (PSD) in wet abrasive slurries. This will play a vital role in optimising processes for fine-polishing of metals in two STFC-funded projects, and materially enhance UK capability to meet instrumentation requirements of the British and International Science Base. This embraces optics for telescopes and instruments for astronomy from microwaves to X-rays, high-power laser systems, synchrotron mirrors and other applications besides.
The first project involves the very difficult challenge of polishing soft materials such as aluminium, used for mirrors in ground-based and space astronomy and many other applications. The second concerns hard materials such as complex moulds and dies in tool-steels, used for industrial mass production. The specific case of 'electroless nickel' falls on the boundary between the projects - it is a hard metal coating, sometimes applied as a thin layer to aluminium mirrors for ease of polishing and increased durability, or on moulding dies to replicate the thin shell-mirrors used for X-ray imaging.
In developing these processes, there is a key property of abrasive polishing slurries about which we currently have no information:- the distribution of the sizes of the abrasive particles. Is there a hard-maximum size, or are there a few larger particles that can damage surfaces? Do particles in working slurry clump together ('agglomerate'), or break up ('fragment'), or do larger particles settle out, and what is the role of agitation in achieving a uniform population of particles? And of great importance, does the slurry become contaminated with anything that could disturb the polishing process (e.g. degrade surface-roughness, cause scratches or digs, etc). There is another consequence of a change in PSD during polishing on any material be it metal, glass or glass-ceramic - it can change the rate of material removal, and this is believed to be one reason why processes are not fully predictable. This in turn impacts the time, cost and indeed risk of manufacture.
The instrument we have selected is both economic and versatile. It can be used in two ways: first, it can measure undiluted slurries as they pass through the return pipe of our recirculating slurry management system. This will give real-time data on the slurry PSD. Second, it can be deployed on the bench with a sample container - very suitable for periodically assessing small samples of specialist slurries which are not recirculated, but used in a "total-loss" system. Given that fine polishing abrasives are typically 2 micron in size or less, the selected instrument can measure over a very suitable range of particle sizes - from about ten microns down to about a nanometre (~10 atoms!). It promises to provide a wealth of fundamental data on processes, which is currently beyond the reach of both ourselves and many other workers in the field. This will add a new dimension to our basic understanding of how processes operate, help us to stay ahead of the competition, and enable superior and cost-effective processes to be developed.
The first project involves the very difficult challenge of polishing soft materials such as aluminium, used for mirrors in ground-based and space astronomy and many other applications. The second concerns hard materials such as complex moulds and dies in tool-steels, used for industrial mass production. The specific case of 'electroless nickel' falls on the boundary between the projects - it is a hard metal coating, sometimes applied as a thin layer to aluminium mirrors for ease of polishing and increased durability, or on moulding dies to replicate the thin shell-mirrors used for X-ray imaging.
In developing these processes, there is a key property of abrasive polishing slurries about which we currently have no information:- the distribution of the sizes of the abrasive particles. Is there a hard-maximum size, or are there a few larger particles that can damage surfaces? Do particles in working slurry clump together ('agglomerate'), or break up ('fragment'), or do larger particles settle out, and what is the role of agitation in achieving a uniform population of particles? And of great importance, does the slurry become contaminated with anything that could disturb the polishing process (e.g. degrade surface-roughness, cause scratches or digs, etc). There is another consequence of a change in PSD during polishing on any material be it metal, glass or glass-ceramic - it can change the rate of material removal, and this is believed to be one reason why processes are not fully predictable. This in turn impacts the time, cost and indeed risk of manufacture.
The instrument we have selected is both economic and versatile. It can be used in two ways: first, it can measure undiluted slurries as they pass through the return pipe of our recirculating slurry management system. This will give real-time data on the slurry PSD. Second, it can be deployed on the bench with a sample container - very suitable for periodically assessing small samples of specialist slurries which are not recirculated, but used in a "total-loss" system. Given that fine polishing abrasives are typically 2 micron in size or less, the selected instrument can measure over a very suitable range of particle sizes - from about ten microns down to about a nanometre (~10 atoms!). It promises to provide a wealth of fundamental data on processes, which is currently beyond the reach of both ourselves and many other workers in the field. This will add a new dimension to our basic understanding of how processes operate, help us to stay ahead of the competition, and enable superior and cost-effective processes to be developed.
