ADOPTIC a new approach - web tool for ceramics additives selection
An European Framework 6 project has resulted in a new approach to additive optimisation in ceramics. Phil Jackson from the UK's Materials Knowledge Transfer Network, reports
Ceramics are one of a number of materials typically processed as powders. More specifically, their processing tends to proceed via an aqueous or non-aqueous powder suspension. Additives, often organic in nature, are employed to control powder suspension rheology as well as intermediate and sintered product properties. While used at relatively low wt% levels (typically 0.1-5wt%), additives such as binders, deflocculants and lubricants help maximise production rates, reduce energy consumption associated with drying/firing, raise yields, and deliver (through microstructure control) critical end properties such as strength, and chemical/abrasion resistance.
Researchers at CERAM Research Ltd, Staffordshire, UK, recognised that small-to-medium enterprise (SME) ceramic producers were disadvantaged compared with larger companies when it came to selecting and optimising additives. Faced with a bewildering array of chemistries and trade names, smaller companies often rely on hearsay, a limited understanding of datasheets and laborious trial and error studies.
In response to this, CERAM pulled together a consortium of European research providers, and industrial SMEs and associations to create a European Framework 6 R&D project targetting SME needs. Additives for Optimisation for Improved Ceramics (ADOPTIC) aimed to develop an electronic knowledge system to aid in additive selection. It also set out to create simple rheology tests and protocols to allow robust in-house appraisal of any additives identified. Finally, the programme intended working with each SME partner on a one-to-one basis to solve specific processing challenges.
The three-year ADOPTIC project began in September 2006. With less than six months remaining, work is focusing on completing population of the knowledge system and training SMEs in additive selection.
Users of the knowledge system have three ways to access it. Firstly, if the user has a good knowledge of additives, it is possible to click the ‘additives’ prompt (see screenshot top, left) and access tree diagrams (see screenshot bottom, left) that divide according to aqueous or non-aqueous systems, generic additive type (deflocculant, binder etc.) and chemistry. General data sheets then advise on typical percentage weight levels used, suppliers, the impact of the additive on suspension and product properties.
Secondly, users can follow typical process routes for various ceramic sub-sectors by clicking on the relevant tab. Information on the additives employed at each stage is shown. Thirdly, a ‘Faults’ section contains a list of processing faults with associated images, descriptions and an indication of additives that can help. Links to additive tree diagrams are available.
The knowledge system is not a substitute for trial work. Having identified a potential additive, users are encouraged to carry out their own optimisation trials. To assist this process, the knowledge system contains information on rheology tests for powders, fluid suspensions and plastic deformable ceramic compositions. The experiments selected employ simple, low cost equipment that SME companies are likely to have access to. Protocols, describing how to carry out reproducible testing, are also included.
Involving individual partner SMEs in the development and application of the knowledge system is an important part of the project. Four UK SMEs are participating in ADOPTIC.
Commercial Clay Ltd is a secondary raw material supplier to the traditional ceramics sector, based in Stoke on Trent. Using bought-in clays, feldspars and commercial clay, it blends materials to form fluid suspensions and plastic bodies that are ready for immediate factory processing.
One issue faced by the company was a request for clay bodies containing powdered glass. A fluid suspension containing the glass powder possessed a rheology that drifted with time. Using zeta potential, rheology and inductively coupled plasma measurements, CERAM showed that ions leaching from the glass powder were deflocculating the suspension. Thus, electrolyte ions were acting as unwanted additives. By applying hydrocyclone washing, CERAM stabilised clay suspensions containing glass. This is shown in the chart (above, right) where torsion viscometry was employed to show deflocculation trends.
International Syalons Ltd is an advanced ceramic company based in Newcastle-Upon Tyne. As a supplier of components based on a Si-Al-O-N chemistry, the company typically buys in powder feedstock ready to press/sinter. The company wanted to use the ADOPTIC project to identify binder additives and assess their performance in granulate powder fabricated in-house.
In selecting a binder or binder blend, a number of properties need to be balanced. Although the green (pressed but pre-sintered) strength of components is important, the effect of binders on suspension rheology (prior to spray drying), granulate flow into dies, and final sintered density also needs consideration.
While studies within the ADOPTIC project are yet to be completed, International Syalons has already identified areas of production where an intermediate sintering stage could potentially be avoided due to improved green strength, saving 30,000 euros per annum. The ability to press more complex shapes could open up new market opportunities.
While the exploitation route is still being finalised, it is likely that access to the electronic knowledge system, which is password-protected, will be free. This will ensure maximum use is made of the website, providing useful information to ceramic producers and generating feedback.
Further information: ADOPTIC