Nanostructured Advanced Ceramics (NASTRAC)

Lead Research Organisation: Loughborough University
Department Name: Materials

Abstract

The goal is to manufacture bulk advanced ceramic components with significantly enhanced properties delivered via retaining a nanostructure. Uniquely, this will be achieved using largely conventional processing routes. Advanced ceramic components, currently worth 17B worldwide, play an enabling role across many sectors; this project will focus on 2 case studies (i) in the electroceramics, viz. pacemakers (medical), digiboxes (telecommunications) & printed circuit boards (combat aircrafts), and (ii) structural ceramics fields, viz. drilling valve components (power stations) and catalytic convertors (automotive), with inputs along the supply chain. Work will involve applying patented novel technology to create high solids content suspensions. Following conventional shaping, novel firing schedules, including microwave-assisted firing, will be used to ensure the nanostructure is retained. The final components will be assessed in actual industrial applications.Two benefits are envisaged from realising a nanoceramic, viz. the ability to use smaller components whilst retaining comparable properties and/or the achievement of superior end properties. The end benefits will thus be light-weighting / miniaturisation / multi-functionalisation of products and a reduction in raw material consumption and recycling, or increased market share through sales of superior products that may well also be more durable, thus assisting in waste minimisation. The project will run for 3 years and commence with a year of basic science (BASS2B) whilst years 2 and 3 will see more applied studies (APPS2B). In year 1 patented technology for concentrating nanopowder suspensions developed for ZrO2 will be applied to BT and optimised for both ceramics (WP1). The goal will be suspensions with solids contents =30 vol% but viscosities of <0.2 Pa s. In year 2 the rheology of both powder suspensions will be optimised for the current factory process routes of screen printing, with the drying step also being optimised, and spray freeze drying of granulate combined with die and isostatic pressing. Sintering techniques for the nanoceramics will include microwave hybrid firing with optimisation being achieved. All of the materials produced will be fully characterised at every step of the process (WP2). In addition, the dopant levels in the two ceramic materials will be optimised to achieve the best properties in the final, sintered products (WP3). Larger-scale quantities of inks for screen printing (BT) and freeze dried nano-suspensions for pressing (ZrO2) will be prepared to allow factory pilot trials (WP4) to take place at Syfer and Dynamic Ceramic (DC) respectively. Year 3 will begin with any optimisation of the processing conditions for the suspensions and granulate (WP5) based on the feedback from WP4 .Further, pilot scale trials at Syfer and DC (WP6) will deliver components that can be evaluated in-service by Selex and Valve Solutions (VS) respectively in end-products, yielding the ability to quantify the level of improvement achieved by the nanostructured ceramics over existing, conventional materials.

Publications

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Description The major goal was to manufacture bulk advanced ceramic components with enhanced properties delivered via retaining a nanostructure. Uniquely, this was achieved largely using processing routes available on industrial floors. Advanced ceramic components, currently worth £17B worldwide, play an enabling role across many sectors; this project was focussed on 2 case studies (i) electroceramics (used in pacemakers, digiboxes etc), and (ii) structural ceramics (used as valve components). First, by adapting patented technology, high solids content nano ceramic suspensions were prepared. Following shaping, novel firing schedules, including microwave-assisted firing, were used to ensure the fine microstructure is retained. The components were then assessed. Zirconia (YSZ) and Barium titanate (BT) were taken as candidate materials.

- Achievements in YSZ

* High solids content, low viscosity nano ZrO2 (n-YSZ) suspensions that were suitable for slip casting and spray freeze drying (SFD) were prepared. Fully crushable and flowable SFD granulates were obtained by adding combustible additives during the process. Homogeneous green bodies were prepared using both the wet and dry processing routes. Hybrid sintering processes (combination of microwave and conventional methods) were optimised to retain nano grain sizes with >98% densification.

* 3% yttria doped nano zirconia (n-3YSZ) was found to have >500 times superior hydrothermal aging (HTA) performance compared to micron counter-parts. The remarkable HTA resistance of n3YSZ was retained even at 90% sintered densities; something that is hitherto unheard of with micron samples -an attribute very useful for biomedical applications; a new TSB project (worth £0.7M) resulted from this.

* 1.5% Yttria doped nano sample was found to have superior toughness compared to micron samples of same composition.

* Scale up quantities of SFD powders suitable for industrial pressing trials were prepared, large components were fabricated and subjected to slurry erosion and cavitation tests. Zirconia showed 6 fold improvement compared to commonly used stellite-coated stainless steel specimens.

* Investigations into the scaling-up of the nano YSZ suspension production was performed by the industrial partners. They have now scaled up the process to make 1 tonne suspension throughput.

- Achievements in BT

* A novel microwave assisted synthesis route for the production of nano sized modified BT formulations has been developed.

* ~60 wt% nano BT inks suitable for screen printing of MLCCs were prepared using non-aqueous media and commercial nano BT powders. The rheology was optimised to make it comparable with that of the industrial bench mark sub-micron BT inks.

* Pilot scale screen printing of MLCCs at the partner site were successfully achieved for assessments.

* Screen printing trials showed good printability however few electrode layers showed wavy patterns. The samples were sintered using conventional, microwave and hybrid techniques to the required density.

* The n-MLCC chips provided advantages such as lower sintering temperature (and the possibility of using cheaper electrodes), acceptable electrical properties in most cases and remarkable improvements in some cases (subject of a patent application). However finer particles resulted in slightly poor dispersion characteristics and K values which will be addressed in future collaborative projects.
Exploitation Route In conclusion we believe that sufficient progress has been made in the NASTRAC project to stimulate interest / raise confidence amongst other advanced ceramic producers who wish to apply the same processing approaches to create nano-structured version of alternative, non-competitive, advanced ceramics such as piezo-electrics, varistors, Pb-free thermistors, Garnet & ZTA based ceramic armours for ballistic protection etc.

As well assisting other academic researchers, the work has the potential to deliver industrially-viable routes to the ceramic manufacturing sector and, hence, useful components to their end-users from a wide range of industries including the automotive, aerospace, electrical, electronic, power generation, security and transport industries. In addition powder suspensions are also used in paints and catalysis. Since these sectors have also exhibited interest in nanotechnology, the work undertaken here will be directly relevant. Similarly, the pharmaceutical industies utilise die pressing extensively and are also interested in nanoparticulates, hence the work on freeze granulation and die pressing will be of direct relevance to them. The results could well prove to be of direct benefit to other particulate-based sectors, including those involving powder metallurgy, hard metals and magnets.

There will also be a number of economic and sustainability benefits, for example: Environmental benefits: product minaturisation will reduce both initial raw material and end of life tonnages; Health benefits: e.g. from less intrusive surgery via smaller, more reliable medical devices, the potential for stronger, tougher bulk ceramics and coatings to be used in applications such as bone replacement. Durable nanostrucrtured ceramic implants could help address the issue of an ageing polupation and the need to keep people physically active for longer; Economic benefits: via component longevity and reliability reducing down-time for replacing worn and failed components. In terms of delivery, clear process routes have been identified for converting nano-powders to nanostructured products. Whilst not yet optimised, actual components (multi-layer ceramic capacitors for barium titanate; valve inserts for zirconia) were fabricated during the project.

For zirconia, a key benefit discovered was the fact a sintered zirconia featuring grain sizes of <~180nm has phenomenal hydrothermal ageing (HTA) resistance properties. Normally, water induces a change in crystal type (tetragonal to monoclinic). This in turn is associated with a volume change that has a catastrophic effect on mechanical strength. A further, unexpected, finding from NASTRAC was that HTA-resistance persists even in structures containing 5-10% porosity. This stimulated the partners MEL, Loughborough University and Ceram to apply for further TSB funding with a new partner Morgan Technical Ceramics. The new project, ZIRCIMP (worth £0.7M) approved and started in October 2011) aims to apply properties to create ceramic hip-replacements that are more durable. This in turn addresses the issue of an ageing population and the need to keep people physically active for longer.

MEL also discovered that the ability to create and the concentrate nano-zirconia suspensions has opened up opportunities to enhance sales to alternative markets (e.g. wash-coats for catalytic convertors). MEL and Loughborogh University are colloborating further on technology transfer issues through additional KTA funding.

For nano-zirconia the field trials featuring nano-zirconia inserts in valves will continue during 2012 as these are long term tests, at the expense of the relevant partners. If improved abrasion resistance and hydrothermal ageing is demonstrated, then Valve Solutions will be able to sell superior "components" commanding a higher price. This in turn will mean sub-contracting to Dynamic-Ceramic Ltd for the production of the pressed, sintered nano-zirconia inserts.

For barium titanate we believe that new commercial capacitor products could well emerge following further research. Two barriers remain for commercialisation in this case: Firstly nano-particles affect the ink rheology significantly, such that the screened ink layers are "wavy". Secondly, whilst encouraging novel electrical properties have been demonstrated, the di-electric constant of the nano capacitor is found to be low. Loughborough University and Syfer Technology have already outlined potential solutions as follows:

(i) To overcome the di-electric constant problem, Loughborough University have already demonstrated that introducing neodymium to modify the barium titanate shell chemistry gives improvements. (ii) To improve ink rheology, a project involving experts in non-aqueous inks and surfactants (e.g. the paint industry) should be initiated.



Overall an estimated 2-years of further R&D has been deemed to offer a good chance of delivering solutions that would position Syfer Technology to consider commercialisation of new capacitor offerings. Loughborough University and Syfer are currently considering the different options for progressing this R&D work (Sponsorship of PhD students; EPSRC, TSB and KTP funding schemes etc.).



Three possible new Intellectual properties were identified:

1) Nano-barium titanate components with key electrical (XR7, XR8) properties that can be sintered at lower temperatures (and so requiring lower cost electrode materials). This is 50/50% owned by Syfer and Loughborough. Syfer will be granted an exclusive licence to fabricate / sell any novel capacitors emerging with Loughborough gaining royalty / licence fees (to be agreed).

2) Scaled-up concentration of nano-powder slurries. This is owned by MEL and Loughborough with a licence agreement signed between them in Feb 2012.

3) Improved abrasion, erosion and corrosion resistance in nano-zirconia. Based on feedback from field trials (due by the end of 2012) decisions on patenting will be made. It is also believed the dental industry may be a beneficiary of this IP.



The dissemination activities were also very strong throughout the NASTRAC programme: 1 keynote and 5 invited international presentations; 8 posters; 8 refereed publications. More publications are planned subject to patent and sponsor's clearance.
Sectors Aerospace, Defence and Marine,Chemicals,Education,Electronics,Energy,Environment,Healthcare,Transport

URL http://www.ceram.com/materials/ceramics/nastrac-project/
 
Description The research outcomes enhanced the understanding related to the safe processing and handling of nanostructured advanced functional ceramic materials (zirconia and barium titanate based ceramics) in academia and industry.
First Year Of Impact 2011
Sector Aerospace, Defence and Marine,Chemicals,Education,Electronics,Energy,Healthcare
Impact Types Societal,Economic

 
Description Brian Mercer Feasibility Award from RS
Amount £29,375 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2009 
End 07/2010
 
Description EP/I500227/1 -- Colloboration fund
Amount £100,780 (GBP)
Funding ID EP/I500227/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2010 
End 12/2011
 
Description EPSRC project on understanding and developing ceramics armour: EP/G042675/1
Amount £415,906 (GBP)
Funding ID EP/G042675/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2009 
End 02/2013
 
Description Grand Challenge
Amount £4,000,000 (GBP)
Funding ID EP/N010493/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2016 
End 02/2021
 
Description Knowledge Transfer Partnership
Amount £232,234 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 06/2017 
End 06/2020
 
Description Loughborough University
Amount £12,983 (GBP)
Funding ID KTA fellowship 
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 11/2012 
End 01/2013
 
Description Loughborough University
Amount £51,570 (GBP)
Funding ID PhD studentship 
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 06/2010 
End 06/2013
 
Description Loughborough University
Amount £8,487 (GBP)
Funding ID Bridging funds 
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 07/2012 
End 10/2012
 
Description Loughborough University EPSRC Pathways to Impact and Syfer Technology Ltd LEGEND project
Amount £82,800 (GBP)
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 12/2012 
End 11/2013
 
Description Loughborough University KTA: Nanoceramics for Dental Applications
Amount £48,312 (GBP)
Funding ID KTA fellowship 
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 07/2011 
End 07/2012
 
Description Loughborough University Project on Processing of Nanocrystalline Transparent YAG Ceramics
Amount £51,570 (GBP)
Funding ID PhD Studentship 
Organisation Loughborough University 
Sector Academic/University
Country United Kingdom
Start 09/2010 
End 09/2013
 
Description MEL Chemicals
Amount £35,000 (GBP)
Funding ID PhD sponsorship 
Organisation MEL Chemicals Inc 
Sector Private
Country United States
Start 06/2010 
End 06/2013
 
Description Morganite Electrical Carbon Ltd.
Amount £45,000 (GBP)
Funding ID PhD sponsorship 
Organisation Morgan Advanced Materials 
Department Morganite Electrical Carbon Ltd
Sector Private
Country United Kingdom
Start 06/2010 
End 06/2013
 
Description TSB project Number: TP 5982-45059
Amount £206,020 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 09/2011 
End 05/2014
 
Description Technology Strategy Board Water Security - MICROCAT project TS/K002783/1
Amount £123,018 (GBP)
Funding ID 101336 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 03/2013 
End 03/2016
 
Title DEFORMABLE GRANULE PRODUCTION 
Description A method of forming granules, the method including forming a suspension of a nanopowder such as a nano zirconia powder containing yttria. The powder is formed from a suspension, and freon is added directly to the suspension as an additive. The suspension is then granulated by spray freeze drying, and the freon subsequently removed by heat treatment. The voids left by the vacated freon provide meso, micro and macro flaws or structural defects in the granules. 
IP Reference US2011241236 
Protection Patent application published
Year Protection Granted 2011
Licensed No
Impact This discovery that was originally developed for zirconia ceramics is successfully employed for a number of nanoceramic systems such as YAG, Alumina, Zirconia Toughened Alumina etc.
 
Title DEFORMABLE GRANULE PRODUCTION 
Description This is an EU patent related to the Spary Freeze Drying of flowable and crushable nanoceramic granules for producing engineering components. 
IP Reference EP2346951 
Protection Patent application published
Year Protection Granted 2011
Licensed Commercial In Confidence
Impact It has opened up a new collaborative opportunity with world leading dental component company in Liechtenstein. This is because this patent has covered that part of the globe also and got noticed.
 
Title DOPED ZIRCONIA CERAMIC 
Description The present invention provides the use of a doped zirconia ceramic having a mean grain size of about 190 nm or less and consisting of the tetragonal zirconia crystallographic phase as a hydrothermally stable material or in an application that requires the use of a hydrothermally stable material. The present invention also provides a doped zirconia ceramic having a mean grain size of about 190 nm or less and consisting of tetragonal zirconia which does not undergo detectable tetragonal to monocli 
IP Reference EP2364282 
Protection Patent application published
Year Protection Granted 2011
Licensed No
Impact This has open up a huge interest in the nanostructed zirconia and other ceramics developed at Loughborough University and many companies have shown keen interest to engage with the Advanced Ceramics group for project colloboration in their respective fields such as defence, electronics, energy and healthcare sectors.
 
Description Press Release and Ceramics Expo 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Through a spin-off project with one of the Nanoplants partner Morgan Advanced Ceramics - the hydrothermal testing protocols we developed have been adopted recently to perform accelerated tests to predict product lifetime of metal and ceramic reflective block sensors used in next generation ultrasonic smart flow meters - a trait that is extremely helpful to design them and reliably measure fluid flows in domestic as well as industrial situations (see press release: http://www.dpaonthenet.net/article/107091/Industry-and-Academia-go-with-the-flow.aspx ). This developed product also planned for showcase at Ceramics Expo 2017 in USA (see: http://www.ceramicsexpousa.com/resources/news/2016/12/14/morgan-announces-ceramic-acoustic-reflector-manufacturing-capability-for-flow-metering/ ).
Year(s) Of Engagement Activity 2015,2016
URL http://www.dpaonthenet.net/article/107091/Industry-and-Academia-go-with-the-flow.aspx