In 2008 Lux Research predicted that nanoparticles would “touch” $3.1 trillion worth of products across the value chain by 2015, with the intermediates market reaching a net worth of $432 billion. Transparent conductive films alone would be worth $3.5 billion by 2020. However, it is almost impossible to find credible predictions for the market potential of the nano-enabled industry beyond 2025. Hence in 2016, it is also fair to say that nanotechnology is still a developing market with many emerging sectors. There are many different methods for producing nanomaterials to meet market demands, and dry methods (despite all the ensuing issues over safety) have been the most successful to date. As alternatives emerge, it is likely that industry will turn away from these dry products and engage with process technologies that can produce a dispersion based, higher quality and easy to formulate product. The real challenges for new alternatives are clearly around material quality, scale up, formulation and (most importantly) the cost of production. 

Continuous hydrothermal synthesis is relatively new technology and would offer a true alternative to other production methods because it is a genuinely continuous process which is also chemically more benign. Continuous hydrothermal synthesis produces nanoparticulate materials by mixing superheated or supercritical water flow with an aqueous flow containing a dissolved metal salt. i.e. rather than slowly heating the entire contents of a batch vessel (batch hydrothermal synthesis), two fluids are continuously mixed together. The problems around this process were solved during research work at The University of Nottingham and the reactor configuration necessary for continuous production was demonstrated at bench (g/hr) and pilot scale (kg/day) prior to the start of the project.

Through the SHYMAN project and the interaction of the 17 partners from across Europe, the process has now been scaled to 1000 tons per year production (dry weight equivalent) which makes the plant the largest multi nanomaterial production facility in the world. Sustainability credentials and cost analysis were also assessed, to compare the process against alternative methods and against existing products in the market place. The process was shown to be highly sustainable, and cost effective with OPEX costs of below 10 euros per kilo (and less than 5 euros, in some cases). A water treatment strategy was devised and implemented that would allow the plant to operate continuously whilst formulating products, ready for sale.

Case studies were part of the project in order to validate the products in the context of real products. These products were selected to demonstrate the efficacy of the process in different areas from healthcare to printed electronics. Each area required particularly performance criteria that would test how controllable the process was in terms of product quality. Bone materials (such as Hydroxapatite) with metal nanoparticles (such as Pt, Ag, Au) for medical diagnostics, printed electronics materials (such as ITO, QD’s), functional lubricants (such as sulphides), ceramic and catalysts nanoadditives for polymers (such as TiO2, and SiO2), doped luminescent ceramics (such as YAG:Ce), superhydrophobic materials (such as CeO2 and SiO2), and functional polymer additives (e.g. UV resistant materials like ZnO and flame retardants).

Continuous hydrothermal synthesis is still in its infancy, in terms of the scope of materials that can be produced and the control over particle size and shape. The project also allowed researchers to specifically focus on expanding the ‘repertoire’ of the process. Partners were able to demonstrate how metals, mixed metal oxides, sulphides, perovskites, phosphates and even metal organic frameworks could be produced. In addition to simple ‘production’, much of the work was around how the size and shape of the products themselves could be altered by changing process variables e.g. pressure, temperature, flow, concentration and precursor type. Most of this work is now published, with a significant number of publications in preparation.

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