R Frischknecht
email: frischknecht@treeze.ch

H Birgisdottir

Ch U Chae

T Lützkendorf

A Passer

E Alsema

M Balouktsi

B Berg

D Dowdell

García Martínez

G Habert

A Hollberg

H König

S Lasvaux

C Llatas

Nygaard Rasmussen

B Peuportier

L Ramseier

M Röck

Soust Verdaguer

Z Szalay

R A Bohne

L Bragança

M Cellura

C K Chau

M Dixit

N Francart

V Gomes

L Huang

S Longo

A Lupíšek

J Martel

R Mateus

C Ouellet- Plamondon

F Pomponi

P Ryklová

D Trigaux

W Yang

Comparison of the environmental assessment of an identical office building with national methods

The IEA EBC Annex 72 focuses on the assessment of the primary energy demand, greenhouse gas emissions and environmental impacts of buildings during production, construction, use (including repair and replacement) and end of life (dismantling), i.e. during the entire life cycle of buildings. In one of its activities, reference buildings (size, materialisation, operational energy demand, etc.) were defined on which the existing national assessment methods are applied using national (if available) databases and (national/regional) approaches. The "be2226" office building in Lustenau, Austria was selected as one of the reference buildings. TU Graz established a BIM model and quantified the amount of building elements as well as construction materials required and the operational energy demand. The building assessment was carried out using the same material and energy demand but applying the LCA approach used in the different countries represented by the participating Annex experts. The results of these assessments are compared in view of identifying major discrepancies. Preliminary findings show that the greenhouse gas emissions per kg of building material differ up to a factor of two and more. Major differences in the building assessments are observed in the transports to the construction site (imports) and the construction activities as well as in the greenhouse gas emissions of the operational energy demand (electricity). The experts document their practical difficulties and how they overcame them. The results of this activity are used to better target harmonisation efforts.

Introduction

One major cause of greenhouse gas emissions (GHG), primary energy demand and environmental impacts is the construction of buildings and their operational energy demand for heating and cooling [START_REF]EEA 2013 Environmental pressures from European Consumption and Production: A study in integrated environmental and economic analysis[END_REF][START_REF] Hertwich | Impacts of Products and Materials: Prioritization and Improvement Options)[END_REF][START_REF] Tukker | Environmental Impact of Products (EIPRO): Analysis of the life cycle environmental impacts related to the final consumption of the EU-25[END_REF][START_REF]UNEP 2009 Buildings and climate change: a summary for decision-makers[END_REF]. To support decision making in reducing environmental impacts, it is important to quantify the impacts and show opportunities for optimization. Environmental life cycle assessment (LCA) is commonly used to assess the environmental impacts of buildings during production, construction, use (including repair and replacement) and end of life. The LCA approach is standardized in ISO 14040 and 14044 [START_REF]) 2006 Environmental management -Life cycle assessment -Principles and framework[END_REF][START_REF]) 2006 Environmental management -Life cycle assessment -Requirements and guidelines[END_REF]. In addition, there are European standards (EN15978 [START_REF]:2011 -Sustainability of construction works -Assessment of environmental performance of buildings -Calculation method[END_REF] and EN15804 [START_REF]2013 -Sustainability of construction works -Environmental product declarations -Core rules for the product category of construction products (Brussels: European Committee for Standardisation (CEN))[END_REF]) for the assessment of environmental performance of buildings and the development of environmental product declarations (EPD) of building products, respectively.

Today, there is disparity in the level of application of LCA on buildings and the existence of LCA databases targeted to the building sector across the world. The international research project IEA EBC Annex 72 focuses on the assessment of the primary energy demand, GHG emissions and environmental impacts of buildings occurring during production, construction, use and end of life. The main objectives of IEA EBC Annex 72 are among others to foster [START_REF] Frischknecht | IEA EBC Annex 72 -Assessing life cycle related environmental impacts caused by buildingstargets and tasks[END_REF]:

 the discussion and harmonisation of methodology guidelines;  the use of environmental information in an early design stage;  the development and use of benchmarks;  the development of national databases targeted to the construction sector.

To be able to establish harmonized methodology guidelines and identify areas of disagreement existing national methods are compared. Reference buildings are defined for that purpose on which the national LCA methods are applied. If available, national databases are used to quantify the primary energy demand, GHG emissions and environmental impacts.

Reference building

The "be2226" office building, located in Lustenau, Austria, is used as a reference building to evaluate existing national LCA methods. The building was designed by the architects Baumschlager Eberle architekten and built in 2013. It is a massive construction and can be seen as a low-tech building. The primary structure consists of pre-stressed and prefabricated concrete ceilings with overlay concrete and 76 cm thick exterior walls in composite masonry. The exterior walls consist of two layers of hollow perforated bricks, whereby the outer bricks are optimised for the insulating effect and the inner bricks bear the loads. The façades are covered on the outside as well as on the inside with lime plaster.

Due to its compact building shape, small and cleverly situated windows and thick exterior walls with a high thermal capacity, neither additional thermal insulation nor active heating and air-conditioning is required. The building is "heated" exclusively by the internal loads from devices and the lighting in combination with the heat dissipation of the people 27,28 . A Building Information Model (BIM) of the building was established by TU Graz. Based on this model the amount of building elements and materials required is quantified. The energy reference area of the building is 2421 m 2 . All results shown in this paper are quantified against the energy reference area. The electricity demand for lighting and operating equipment is 196 MJ/m 2 a.

Methods and databases

Used national methods including study period and databases

The assessment of the building was carried out by 22 different institutions using the same material and energy demand but applying different LCA approaches. Within the different approaches the primary energy demand, GHG emissions and environmental impacts were assessed. The focus in this paper is on the GHG emissions. In total 21 different national or regional LCA approaches were applied. The assessments of the be2226 building were carried out by the national experts, and results were reported in a uniform template that allowed for comparison between the countries. The applied methods are mainly used as part of a sustainability assessment and for certification schemes of buildings, design aid and in research activities in the respective countries.

The methods apply different reference study periods. 15 methods use a reference study period of 50 years for this case study 29 and six methods use 60 years. Denmark uses 80 years as reference study period (see Table 1). The reference study period has an influence on the relative importance of the GHG emissions of manufacture, construction, replacements and end of life stages on one hand, and the operational GHG emissions on the other. Furthermore, the methods differ in the used service life of building elements/components and the modelling of the end of life treatment of the materials. In cases the service life of a building element exceeds the reference study period, the reference study period is applied.

Table 1: Overview of the reference study periods and databases used within the LCA methods applied to assess the environmental impacts of the "be2226" building. Building certification schemes and research a https://www.oneclicklca.com/support/faq-and-guidance/documentation/database/, last visited on: 23.5.19 b https://calculatelca.com/software/impact-estimator/lca-database-reports/, last visited on: 24.5.2019

Reference study period [years]

Mostly different versions of the ecoinvent database (i.e. [10-12, 14, 18, 19, 24, 26]) were used to assess the environmental impacts of the building. Some institutions applied country specific databases (see Table 1). The life cycle stages included in the respective approaches are shown in Table 2.

Table 2:

Overview of the life cycle stages included in the applied approaches.

Life cycle stages

A1-A3 A4 A5 B1 B2 B3 B4 B5 B6 B7 C1 C2 C3 C4

GHG emissions of construction materials

A preliminary contribution analysis of the different building elements to the total GHG emissions showed that bricks, concrete, windows and reinforcing steel are important. In Figure 1 the GHG emissions of brick along the life cycle stages (Modules A-D) as defined in EN 15804:2012 [START_REF]2013 -Sustainability of construction works -Environmental product declarations -Core rules for the product category of construction products (Brussels: European Committee for Standardisation (CEN))[END_REF] are presented. Hong-Kong and the Netherlands did not report the emissions according to the life cycle stages. In all countries, which reported the emissions according to the life cycle stages, most of the GHG emissions of bricks are emitted in the product stage. While the GHG emissions in the product stage (A1-A3) of bricks are similar in all countries, differences are observed in the construction process stage (A4-A5). New Zealand reported a substantially higher impact in this life cycle stage than the other countries, mainly due to the large import distances of bricks from Australia to New Zealand (no domestic production). In the end of life stage (modules C1-C4) differences in the results are based on different assumptions on recycling shares, waste processing and final disposal scenarios. Germany reported negative GHG emissions in the end of life stage of bricks. According to the LCA data they use, the treatment in the decomposition phase leads to a complete carbonation of the free alkali-and alkaline earth oxides, which is accounted for as a credit. China assumed a high recycling potential for bricks and therefore reported high negative GHG emissions in the end of life stage. The highest GHG emissions of bricks are reported by Hong-Kong. Over all life cycle stages (i.e. without Module D) and excluding New Zealand and Hong-Kong the GHG emissions of bricks reported by the countries differ by a factor of 1.6.

Figure 1.

GHG emissions of bricks caused in the different life cycle stages in kg CO 2 -eq/kg assessed according the national LCA approaches from the countries listed.

In Figure 2, the GHG emissions in kg CO 2 -eq/kg of concrete are presented. Most of the GHG emissions of concrete are emitted in the product stage. The emissions differ up to a factor of 2.2 between the countries. The main reasons are different energy mixes in clinker production (share of traditional and secondary fossil fuels such as hard coal, lignite, fuel oil and natural gas or used tires), different average shares of clinker in 1 kg cement and different cement contents in 1 m 3 concrete. The GHG emissions in kg CO 2 -eq/kg reinforcing steel are shown in Figure 3. In all country assessments the product stage of reinforcing steel contributes most to the GHG emissions. The highest reported emissions are around 6 times higher than the lowest ones. The main reason is the share of recycled content in the reinforcing steel. The approaches applied in China, France and New Zealand report the net benefits and loads beyond the system boundaries. In China the net benefit is 53 % of the total GHG emissions of reinforcing steel reported for A1-C4. In France, the net benefit amounts to 57 % of the A1-C4 emissions and in New Zealand 8 %.

GHG emissions of electricity mixes

The GHG emissions of the electricity used in operation reported by the different countries differ substantially (see Figure 4). While Denmark, Norway and France report low GHG emissions of their electricity mix, China, Czech Republic, Hong-Kong, Hungary and the Netherlands report comparatively high GHG emissions. The highest reported emissions are 30 times higher than the lowest reported emissions. These differences in GHG emission from electricity reflect the real existing differences in the national electricity supply. Denmark is the only country reporting a future average mix based on renewable energies only. *: value back-calculated from the GHG emissions of B6

Issues encountered during the assessment

During the assessment of the reference building the authors of this paper encountered several issues with the provided data. Most of the issues were related to missing life cycle inventory data for specific materials, such as "vacuum insulation panels" and different aggregation stages in the information provided and the data available. The issue encountered with the aggregation level concerned the product level (e.g. reinforced concrete, instead of having separate LCI data on concrete and reinforcing steel) and the life cycle stages (e.g. data only available for the whole life cycle and not for Modules A, B and C separately). Furthermore, differences in the units of the building data and the available LCA data occurred (e.g. pieces vs. m 3 of stairs). To overcome the limitations of lacking LCI data for materials the authors used proxies, EPDs or did not consider the material and building elements at all (e.g. elevator).

Preliminary results: greenhouse gas emissions caused by the be2226 building

The preliminary results of the assessment of the GHG emissions caused by the manufacturing, construction, use and end of life of the reference building "be2226" are presented in Figure 5. The total GHG emissions reported are between 10 and 71 kg CO 2 -eq/m 2 a depending on the national approach used.

Figure 5.

Greenhouse gas emissions in kg CO 2 -eq per m 2 and year of the reference building "be2226" assessed according to the national/regional approaches of the countries listed (preliminary results). Different life cycle stages were taken into account depending on the national approaches (see Table 2). Most of the countries were able to report the GHG emissions according to the life cycle stages defined in EN 15804:2012 [START_REF]2013 -Sustainability of construction works -Environmental product declarations -Core rules for the product category of construction products (Brussels: European Committee for Standardisation (CEN))[END_REF] and EN 15978:2011 [START_REF]:2011 -Sustainability of construction works -Assessment of environmental performance of buildings -Calculation method[END_REF]. Hong-Kong and the Netherlands reported the emissions of modules A4, A5, B, C and D all together in the product stage (modules A1-A3) except the operational energy use (B6)30 . The product stage was assessed by all countries and varies between 5.7 and 15 kg CO 2 -eq/m 2 a. Within the product stage the GHG emissions vary by a factor of 2.6 (excluding Hong-Kong). The transport to site and the construction and installation process (construction process stage A4 and A5) was addressed by 13 approaches. Over all countries those life cycle stages vary between 0.3 and 3.1 kg CO 2 -eq/m 2 a.

All national approaches, except Portugal and Sweden took the replacement (B4) of materials and building elements into account. However, only few approaches consider the maintenance (B2), repair (B3) and refurbishment (B5). Overall, the use stage (B2-B5) varies between 0.1 and 5.2 kg CO 2eq/m 2 a. A very high variability can be seen in the contribution of the operational energy use stage. It directly reflects the differences in GHG emissions of the electricity mixes (see Section 3.3) because electricity is the only energy carrier used in operation. The end of life stages (C1-C4) vary between 0.2 and 2.4 kg CO 2 -eq/m 2 a. This variation is not linked to the scope of end of life stage modules considered. Net benefits and loads beyond the system boundary were reported by six approaches out of 21. The approach applied in the Netherlands includes energy recovery from waste incineration and product reuse or recycling. However, the net benefits are not reported separately in the Dutch assessment. Where reported separately, the benefits are between 0.1 and 3.7 kg CO 2 -eq/m 2 a.

Discussion

In all assessments, most GHG emissions occurred either in the product stage or during the operational energy use. The differences in the operational energy use are due to the substantial difference in the GHG-intensity of the national electricity mixes. The variance of the GHG emissions occurring in the product stage is due to the different GHG emissions of the construction materials (see Section 3.2) and to the differences in the reference study period applied. The Danish assessment shows the lowest GHG emissions per m 2 and year. Firstly, a reference study period of 80 years leads to lower annual emissions from the product stage (A1-A5) compared to the reference study period of 50 or 60 years. Secondly, the electricity mix applied during operation is a future national mix based on renewable energies with comparatively low GHG emissions per MJ.

The annual specific GHG emissions of this building are mainly influenced by the GHG intensity of the electricity mix used during operation. The GHG intensity of the construction materials used (Modules A1-A5) as well as the difference in reference study period cause additional differences in the annual specific GHG emissions of the "be2226" reference building. The contributions from the end of life stage are minor. The building hardly uses plastics and plastics-based insulation materials which would give rise for substantial GHG emissions when incinerated. On the building level, the potential loads and benefits beyond the system boundary are hardly visible.

The different applied approaches result in a wide range of the total GHG emissions of the "be2226" building. The differences in the results of the assessments of the "be2226" building are due to the substantially different CO 2 -footprints of the energy carriers and the construction materials rather than methodological differences between the approaches applied. Hence, the relatively large differences are no cause for concern. Depending on the national context low carbon footprint buildings are achieved using different concepts. It is crucial however, that environmental benchmarks for buildings in a country are based on the LCA approaches and LCA databases used in that particular country.

Outlook

The comparison of all the national LCA approaches applied will be used to better target harmonization efforts and identify areas of disagreement. Furthermore, a second reference building, a Chinese highrise building will be assessed by the IEA EBC Annex 72 participants to get a deeper understanding of the different approaches applied on a more complex building. The insights gained from both comparative exercises will be used along with other results of the international research project IEA EBC Annex 72 to develop and extend the methodology guideline on LCA of buildings and life cycle related environmental benchmarks.

Figure 2 .

 2 Figure 2. GHG emissions of concrete during different life cycle stages in kg CO 2 -eq/kg assessed according the national LCA approaches from the countries listed.

Figure 3 .

 3 Figure 3. GHG emissions of reinforcing steel during different life cycle stages in kg CO 2 -eq/kg assessed according the national LCA approaches from the countries listed.

Figure 4 .

 4 Figure 4. GHG emissions of the electricity mixes applied in the assessment of the operational electricity demand (module B6) of the reference building in g CO2-eq/kWh. *: value back-calculated from the GHG emissions of B6

Field of application

		Reference study period	Database	Field of application
		[years]
	DE	50	Ökobau.dat 2018 [16]	BNB
	DK	80	Ökobau.dat 2016 [15]	DGNB Denmark
	ES	50	ecoinvent 2.0 [18]	research
	FR	No official requirement,	ecoinvent 2.2 [19] adapted to French	EQUER
		50 years in this case study,	context
		default value 80 years
	HK	50	Studies and statistics [20-22]	Research
	HU	50	ecoinvent 2.0 [18] adapted to Hungarian	Education and research
			conditions wherever relevant (for
			products primarily produced in Hungary,
			adaptation of the electricity mix and
			natural gas)
	IT	50	Ecoinvent 3.4 [12], EPDs	Research
	NL	50	National Environmental Database for	Building permits
			building products (NMD 2.2) [23] -
			producer-specific data and generic LCA
			data from ecoinvent 3.3 [11].
	NO	60	Ecoinvent 3.3 [11], EPDs	Research, decision-making tool
	NZ	60	NZ whole building whole of life	Certification, research
			framework -materials data developed
			from EPDs for materials and modelling in
			ecoinvent 3.1 [24] (specific process data
			with NZ Grid electricity)
	PT	50	LCIA Database for Portuguese Building	Research
			Technologies [25], based on generic data
			from Ecoinvent 2.1 [26], Ecoinvent
			version 3.3 [11]
	SE	50	Swedish Building Sector Environmental	Building certification schemes
			Calculation Tool (BM) [27]
	UK	50	Database embedded in OneClickLCA a	Building certification schemes
	US	50	Database embedded in ATHENA Impact
			Estimator b
	AT	50	ecoinvent 3.2[10]	Research
	BE	60	ecoinvent 3.3 [11] adapted to Belgian	Research and webtool
			context	(TOTEM)
	BR	50	ecoinvent 3.4 [12] adapted to Brazilian	Research
			context
	CA	60	ecoinvent 3.4 [12] adapted to Canadian	Building certification schemes,
			context and EPDs	EPDs
	CH, ETHZ	60	KBOB LCA data DQRv2 [13]	Building certification schemes
	CH, HES-SO	60	KBOB LCA data DQRv2 [13]	Building certification schemes
	CN	50	ecoinvent 3.5[14]; CLCD-China-ECER	Building certification scheme
			0.8.1, Oekobau.dat [15, 16]
	CZ	50	ecoinvent 3.3 [11], boundary condition	Decision-making tool,
			from SBToolCZ methodology [17]	voluntary certification

https://www.baumschlager-eberle.com/en/work/projects/translate-to-english-projekte-details/2226/ last visited on: 8.3.2019

It could be argued that the internal loads from devices are a free heating source (waste heat) and that their electricity consumption shall not be attributed to the building's operational energy demand. However, for the purpose of this paper (comparing national assessment methods) electricity demand of devices is considered part of the operational energy demand.

D AT X X X X X X X X BE X X X X X X X X X X X X BR X X X X X X X X CA X X X X X X X X X X CH, ETHZ X X X X X X X CH, HES-SO X X X X X X X CN X X X X X CZ X X X DE X X X X X X DK X X X X X ES X X X X X X X X X X X X X FR X X X X X X X X X HK X X X X X X X X X X X X X HU X X X X X X X X X IT X X X X X X NL X X X X X X X X X X X X X

For reasons of confidentiality the Dutch National LCA database comprises only aggregated emissions data for the stages A, B, C and D together, in case of producer-specific LCA data.

Acknowledgments

The authors would like to thank the IEA for its organizational support and the colleagues involved in the project (Members: Australia, Austria, Belgium, Canada, Czech Republic, P.R. China, Denmark, Finland, France, Germany, Italy, R. Korea, the Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom, United States of America, Observers: Brazil, Hungary, India, Slovenia) for their cooperation. Additionally, they would like to thank the organizations and institutions in the participating countries for their financial support.

Life cycle stages


Houssem Sellemi
email: sellemi.houssem@gmail.com

Amor Sandrine Coste
email: sandrine.coste@univ-lemans.fr

Ben Ali

Richard Retoux
email: richard.retoux@ensicaen.fr

Leila Samia Smiri
email: lsmiri@gmail.com

Philippe Lacorre
email: philippe.lacorre@univ-lemans.fr

Amor Benali
email: amor.benali@fsb.rnu.tn

Synthesis of La 2 Mo 2 O 9 powders with nanodomains using polyol procedure

Keywords: A. Powders: chemical preparation, B. Electron microscopy, B. Microstructure-final, B. X-ray methods, D. La 2 Mo 2 O 9

Powders of oxide-ion conductor La 2 Mo 2 O 9 presenting nanodomains were synthesized by using polyol processes. The influence of different process parameters on the structure and particles morphology was determined. By the classical polyol process, whatever the polyol solvent used (ethylene glycol, diethylene glycol, 1,2-propanediol and tetraethylene glycol) platelet particles with dimensions of few hundred nanometers long and around twenty nanometers thick were observed, as agglomerates of small subparticles. Only with diethylene glycol, pure La 2 Mo 2 O 9 was obtained, whereas with microwave assistance, ethylene glycol also leads to pure product. For both ethylene and diethylene glycol solvent, the microwave assisted process resulted in either agglomerates or desert roses conglomerates after heat treatment at 500°C for 5 min or 2h, respectively. Specific surface areas, ranging between 23 and 36 m².g -1 , have been measured for pure La 2 Mo 2 O 9 powders.

Introduction

The current concern for clean energy generation has triggered the development of fuel cells, among which solid oxide fuel cells (SOFCs) are particularly attractive for domestic power and heat co-production. A current challenge is, by finding the most appropriate materials, to lower the operating temperature of such devices in order to reduce the costs and minimize reactivity between the cell core components [START_REF] Jacobson | Materials for Solid Oxide Fuel Cells[END_REF]. La 2 Mo 2 O 9 and derived LAMOX oxide-ion conductors might be suitable candidates due to their high ionic conductivity [START_REF] Lacorre | Designing fast oxideion conductors based on La 2 Mo 2 O 9[END_REF]. La 2 Mo 2 O 9 presents two polymorphic phases: at low temperature the less conducing ordered Į phase is monoclinic, while at high temperature the highly conducing disordered ȕ phase is cubic [START_REF] Goutenoire | Crystal structure of La 2 Mo 2 O 9 , a new fast oxide-ion conductor[END_REF]. The D-E first order phase transition, which occurs at about 580°C, is detrimental to the mechanical stability.

However it can be overcome by appropriate cationic substitutions which stabilize the Ephase down to room temperature [START_REF] Goutenoire | Structural and transport characteristics of the LAMOX family of fast oxide-ion conductors, based on lanthanum molybdenum oxide La 2 Mo 2 O 9[END_REF]. Nevertheless the instability of these molybdates under reducing atmosphere, as well as the very good catalytic properties of La 2 Mo 2 O 9 for the oxidation of propane, make them more suitable as core cell materials for single chamber SOFCs [START_REF] Jacquens | Tests for the use of La 2 Mo 2 O 9 -based oxides as multipurpose SOFC core materials[END_REF]. Indeed their reduction generates the appearance of electronic conductivity, turning them into mixed ionic-electronic conductors (MIEC), which becomes an advantage for application as anode materials in conventional double chamber SOFCs [START_REF] Vega-Castillo | Thermodynamic stability, structural and electrical characterization of mixed ionic and electronic conductor La 2 Mo 2 O 8.96[END_REF]. As a matter of fact, the amorphous reduced form La 2 Mo 2 O 7-G has been shown to be a performing, sulphur-tolerant, anode material [START_REF] Lu | Amorphous ceramic material as sulfur-tolerant anode for SOFC[END_REF].

The studies summarized above show that La 2 Mo 2 O 9 based derivatives have good potentialities for applications as SOFC core materials. Among them, the use as anode materials in conventional SOFC design is the most promising. It requires the elaboration of porous layers with as small particles as possible in order to optimize the gas contact with the MIEC surface.

The most common synthesis method to prepare La 2 Mo 2 O 9 and derivatives is the solid state route, from which most of the properties of these materials have been studied.

Although very simple, this method is both time and energy consuming, since optimal synthesis temperatures are close to 1000°C for at least several hours. Moreover, the large particles obtained by this way are inappropriate for use in the above-mentioned application unless reduced in size, but partly efficient grinding generally induces the introduction of impurities detrimental to the materials properties. In order to overcome the problem, efficient synthetic methods have already been proposed, such as freeze drying [START_REF] Marrero-López | Synthesis, sinterability and ionic conductivity of nanocrystalline La 2 Mo 2 O 9 powders[END_REF] or spray pyrolysis [START_REF] Georges | Microstructure Related Conductivity in La 2 Mo 2 O 9 Ceramics[END_REF]. However these methods remain relatively costly due to the requested equipment. Other, more classical ways have been used, such as the citrate method [START_REF] Marrero-López | Effects of preparation method on the microstructure and transport properties of La 2 Mo 2 O 9 based materials[END_REF], a Pechini or modified Pechini route [START_REF] Zhuang | Sol-gel synthesis and transport property of nanocrystalline La 2 Mo 2 O 9 thin films[END_REF][START_REF] Subasri | Synthesis and characterization of (La 1-x M x ) 2 Mo 2 O 9-G ; M=Ca 2+ , Sr 2+ or Ba 2+[END_REF][START_REF] Zhuang | Ionic Conductivity Enhancement of La 2 Mo 2-x W x O 9 nanocrystalline films deposited on alumina substrates by the Sol-Gel Method[END_REF][START_REF] Wang | Enhancement of conductivity in La 2 Mo 2 O 9 ceramics fabricated by a novel three-stage thermal processing method[END_REF], the microwave assisted method [START_REF] Saradha | Microwave-assisted combustion synthesis of nanocrystalline La 2 Mo 2 O 9 oxide-ion conductor and its characterization[END_REF] and the EDTA complexation method [START_REF] Cheng | Facile synthesis of La 2 Mo 2 O 9 nanoparticles via an EDTA complexing approach[END_REF].

Our aim with the current work is to develop convenient methods which are not too costly, in order to prepare powders with large specific surface area and different morphologies, and to elaborate coatings, both to be used in suitable applications. For this purpose we present here another preparation method, the polyol process, which can lead to various microstructures [START_REF] Larcher | Some insights on the use of polyols-based metal alkoxides powders as precursors for tailored metal-oxides particles[END_REF][START_REF] Škapin | Synthesis and characterization of calcite and aragonite in polyol liquids: Control over structure and morphology[END_REF][START_REF] Joseyphus | Low temperature synthesis of ITO nanoparticles using polyol process[END_REF], control the particles size [START_REF] Flores-Gonzalez | Preparing nanometer scaled Tb-doped Y 2 O 3 luminescent powders by the polyol method[END_REF], and lower the temperature of the heat treatment -generally necessary as a final step when soft chemistry is used.

Material and methods

The polyol process has been investigated through a classical refluxing route or, for comparison, through a microwave-assisted process. In both cases, the following thermal treatments have been realized.

Polyol Process

Precursor salts, La(CH 3 CO 2 ) 3 . and tetraethylene glycol (TEG) (Acros Organics, 99.5%).

The resulting mixture was then heated to reflux under mechanical stirring for 3 hours.

During this process, the initial precursor dissolved totally and the color of the obtained solution gradually changed to white color, and then a white-gray precipitate appeared.

After cooling, the obtained precipitate was washed and dried in air at 60°C for 24 hours.

The obtained powders are called precursors hereafter. Finally, ultrafine La 2 Mo 2 O 9 powders were obtained by flash heat treatments for 5 min or 2 h in a muffle furnace preheated at a fixed temperature ranging from 200 to 900°C. The aim of this flash heat treatment was to avoid any important growth of the grain size. ), and placed in a TeÀon autoclave and heated at 180 °C for 1 h. After cooling, a precipitate was obtained. The same treatments, as for the classical polyol process, were carried out on the precipitate to obtain the La 2 Mo 2 O 9 powders.

Microwave-assisted process

Characterization techniques

The phase purity of the obtained powders was checked by X-Ray powder Diffraction (XRD) analysis. Patterns were recorded at room temperature on a PANalytical ș/ș Bragg-Brentano X'pert MPD PRO diffractometer (CuKĮ radiation) equipped with the X'Celerator detector. The diagrams were collected in the 10-60° scattering angle range.

Fourier Transformed InfraRed (FTIR) spectra were collected in air with an Alpha Bruker spectrometer equipped with an ATR sampling module. Each spectrum was obtained in the 4000-400 cm -1 range.

Thermal analyses were performed on raw precipitates with a TGA/DTA Q600 SDT TA Instruments apparatus (Pt crucibles, Al 2 O 3 as a reference) under air flow (100mL/min).

Thermograms were collected between room temperature and 950°C with a heating/cooling rate of 10°C.min -1 .

Carl Zeiss Supra 55 (Oberkochen, Germany) high resolution scanning electron microscope (SEM) equipped with EDS was used to investigate the morphology.

The transmission electron microscopy (TEM) study was performed using a 200kV

JEOL 2010 FEG transmission electron microscope fitted with a double tilt sample holders (tilts ±42°). Specimens for TEM observations were prepared by crushing powdered samples in ethanol. After dispersion of the crystallites a drop of the suspension is deposited and dried onto a carbon coated copper grid.

The specific surface area measurements were realized according to the BET method with a Micromeritics Tristar II apparatus.

Results and discussion

Effect of heat treatment temperature

This part deals with the powders obtained by the common polyol process (without microwave assistance) in the DEG as solvent. Precursor powder ((P DEG ) was treated at a fixed temperature in the range 200-900°C for annealing time of 5min or 2h. XRD patterns of the precursor, and of the precursor annealed at 200°C for 2h present mainly two peaks around 24.5 and 27.8° (in 2ș) (Fig. 1). These peaks are still present after annealing at 450°C, whereas they disappear after a flash heat treatment at 500°C for 5 min. Moreover, after annealing at 500°C for 5 min, no organic groups are detected by FTIR (Fig. 2). Bands around 1540 and 1405 cm -1 and probably around 630 cm -1 , that could be attributed to nitro groups (NO 2 ), are observed after annealing at 450°C and have quite totally disappeared after a flash heat treatment at 500°C for 5min. The other bands under 1000 cm -1 correspond to inorganic groups (metal-oxygen bonds).

According to these results, the optimal thermal condition in order to obtain pure La 2 Mo 2 O 9 powders with a minimal grain size seems to be a flash heat treatment at 500°C for 5 min. These results are in agreement with the DTA-TG results (Fig. 3) as the entire weight loss of about 35% is reached at around 550°C. The slight difference between this temperature and the one obtained by flash heat treatment can be explained by a difference in temperature between the two furnaces as well as the difference in kinetics between these two heat treatments.

By XRD, as expected, a decrease of the full width at half maximum (FWHM) partially or totally due to an increase of the crystallite size can be observed mainly with temperature increase and more slightly with annealing time, the impact of time being more important at 500°C than at 600°C (Fig. 4). The 2T evolution of the observed FWHM of the most intense peaks, assuming each observed peak as a single (hkl) reflexion (cubic setting), is presented in Fig. 5. The same evolutions for the Į and ȕ-La 2 Mo 2 O 9 phases obtained by the solid state route have been added for comparison. Indeed, one of the differences between the monoclinic and cubic phase XRD diagrams is the presence of small superstructure peaks in the monoclinic D phase. As the FWHM of the peak is very important, these superstructure peaks cannot be evidenced. However another difference originates from the monoclinic peak splitting, which is more or less pronounced depending on the diffraction planes. It was used to identify the nature of the La 2 Mo 2 O 9 phases obtained by the polyol process. The irregular evolution of the FWHM with the diffraction angle, very similar to that of Į La 2 Mo 2 O 9 phase obtained by solid state route, indicates that all the samples obtained by the common polyol process are Į type in nature. This is in agreement with the exothermic peak observed by DTA at around 534°C while cooling down (see Fig. 3), suggesting that at least a part of the ȕ-La 2 Mo 2 O 9 phase transforms into the Į-La 2 Mo 2 O 9 phase [START_REF] Goutenoire | Crystal structure of La 2 Mo 2 O 9 , a new fast oxide-ion conductor[END_REF][START_REF] Georges | Reducibility of fast oxide-ion conductors La 2-x R x Mo 2-y W y O 9 (R = Nd, Gd)[END_REF][START_REF] Corbel | Effects of partial Substitution of Mo 6+ by Cr 6+ and W 6+ on the crystal structure of the fast oxide-ion conductor La 2 Mo 2 O 9[END_REF].

The crystallite size has been estimated, from XRD patterns, according to the Scherrer equation (the contribution of the apparatus on the FWHM being deduced). From the thinner diffraction peak at about 2T=25°, the crystallite size is around 23nm after a flash heat treatment at 500°C for 5 min, and around 143 nm after a heat treatment at 950°C for 2h. No effect of the grain size on the stabilization of the high temperature ȕ-La 2 Mo 2 O 9 phase is thus observed in this work.

In order to determine the morphology and microstructure of the powders obtained and to estimate if the crystallite size measured by XRD corresponds to monocrystallized grains or to particles composed of different crystalline domains, the powders have been observed by SEM (Fig. 6) and TEM (Fig. 7a). After a flash heat treatment of 5 min at 500°C, the powder is composed of platelet particles of few hundred nanometers long and around twenty nanometers thick. This thickness is in agreement with the crystallite size determined previously by XRD. For each treatment, the low magnification SEM observations evidence the high level of homogeneity in grain sizes. The observations of these platelet particles by TEM show that they consist of small domains connected to one another, letting holes between them during the heat treatment (Fig. 7b). When two platelet particles are stick together, the holes are not necessarily aligned. Selected area electron diffraction (SAED) performed on numerous, either isolated or superimosed, platelet particles indicates that the domains that build up the particles are slightly disoriented, as well as the platelet particles relative to each others.

No well defined crystallites are distinguished. However, it can be pointed out that the thickness of the platelet particles is in accordance with the large FWHM of the XRD peaks. By increasing annealing time and temperature, platelet particles sinter until they form large grains of a few micrometers size after a heat treatment at 950°C, leading to narrow XRD peaks, in agreement with a large crystallite size.

Effect of the solvent

Different polyols have been used in order to determine their effect on the grain morphology of the prepared powders. In this section, we focus on powders obtained after a flash heat treatment at 500°C for 2 hours, such a duration allowing an easier observation of possible impurities.

Pure La 2 Mo 2 O 9 is obtained with DEG whereas La 2 Mo 3 O 12 impurity is observed by XRD when used solvent is EG or TEG (Fig. 8). The amount of La 2 Mo 3 O 12 impurity is higher with TEG. The purity of La 2 Mo 2 O 9 obtained with DEG was confirmed by XRD of the precursor heated at higher temperature.

Effect of microwave assistance

The aim of this section is to determine the effect of microwave assistance on the purity and the grain morphology of the precipitate after a heat treatment at 500°C. The microwave assistance has already been successfully used particularly for the synthesis of doped ZnO nanocrystals [START_REF] Hammarberg | Microwave-assisted polyol synthesis of aluminium-and indium-doped ZnO nanocrystals[END_REF].

All the powders obtained using microwave assistance and a heat treatment at 500°C for 2 hours are identified to be pure La 2 Mo 2 O 9 when EG as well as any other of the polyols are used as solvent (Fig. 9). This result is thus very important, since the microwave assistance allows the preparation of pure La 2 Mo 2 O 9 from the solvent with the lower relative toxicity, namely EG. SEM observations evidence a strong difference in morphology when the microwave assistance is used (Fig. 10). Large porous and monodispersed grains (more or less 1 μm in diameter) are observed. Some long and thin crystallites are present at the surface of the grains, and form desert-rose like agglomerates. Moreover, with the microwave assistance, an important evolution of the morphology is observed after a heat treatment at 500°C for 2h compared to 5 min: it seems that the crystallites grow during the heat treatment to give, after 2h, far larger desert roses (around 10 times bigger). This is far different from the classical polyol process for the study made with DEG since in these conditions, no important evolution of the morphology was observed. In addition, by varying the solvent (EG or DEG), the morphology and its evolution with the heat treatment time are similar.

Effect of the different parameters on the specific surface area

The specific surface area, according to the BET method, of the precursors obtained by the classical and the microwave assisted processes with DEG, and by the microwave assisted process with EG and flash treatment at 500°C for 5min, was measured (Table 1). Powders prepared by microwave assistance in DEG exhibit a slightly higher specific surface area. However, in EG, the specific surface area is similar to that obtained with the classical polyol process. This should allow measuring the effect of the morphology on catalysis, the specific surface area being constant.

For comparison, the specific surface areas presented by Kuang et al. [START_REF] Kuang | Preparation and characterization of ultrafine rare earth molybdenum complex oxide particles[END_REF] for La 2 Mo 2 O 9 powders obtained from citrates reach 21.3 m².g -1 with a heat treatment at 500°C for 4h.

In the current work, powders with slightly higher specific surface area have been prepared at the same temperature in a shorter time by using microwave assisted polyol process with DEG.

Conclusions

This work evidences that the polyol process is a simple and efficient way to prepare pure La 2 Mo 2 O 9 materials, without expensive devices. After the dissolution of the starting material, precipitates are formed under reflux. A heat treatment at 500°C only for a short period of time is necessary to obtain pure materials. This temperature is far different parameters (heat treatment temperature and time, nature of the polyol, microwave assistance) on the phase purity, structure and morphology were determined. Agglomerated platelet particles or desert roses composed of nanocrystallites can be obtained. Such morphologies are very promising for applications such as catalysis since they present a high specific surface area, easily reachable by gases. The study of the effect of other parameters used in the polyol process and of the possibility to make cationic substitutions is currently in progress. sity (a.u.)

ϱϬϬΣ ϵϬϬΣ ∇ ∇ ∇ ∇ ͗ ɲ >Ă Ϯ DŽ Ϯ K ϵ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ͍ ͗ ŝŵƉƵƌŝƚLJ
∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ Ϳ Ϳ Ϳ Ϳ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ Figure 8
y (a.u.)

∇ ∇ ∇ ∇ ͗ ɲ >Ă Ϯ DŽ Ϯ K ϵ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ Ϳ ϮϬ ϯϬ ϰϬ Ϯϱ ϯϱ Intensity 2ș (°) ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ ∇ Ϳ Ϳ Figure 9
Diethylene glycol 500°C 5 min

Ethylene glycol 500°C 5min

Diethylene glycol 500°C 2h Ethylene glycol 500°C 2h

La 2

 2 Mo 2 O 9 phase was obtained from the solvothermal reaction by using a microwave oven (CEM Mars). A mixture of La(CH 3 CO 2 ) 3 .1,5 H 2 O (Alfa Aesar, 99,99%) and (NH 4 ) 2 Mo 2 O 7 (Alfa Aesar, 99,99%) was dissolved in 15 ml of DEG or EG ([La+Mo] = 6 0.2 mol.L -1

Fig. 1 :Fig. 2 :

 12 Fig. 1: XRD diagrams of the peak around 2ș =24.5° and of the most intense pseudo-

Fig. 3 :

 3 Fig.3: DTA-TG of the dried precipitate (P DEG ) obtained by the polyol process in DEG.

Fig. 4 :

 4 Fig. 4: XRD diagrams of the most intense pseudo-cubic (210) peak of the dried

Fig. 5 :Fig. 6 :

 56 Fig. 5: Observed FWHM of XRD peaks of the polyol-process made powders heated at

Fig. 7 :Fig. 8 :

 78 Fig. 7: TEM images of the polyol-process made powders heated at 500°C for 5min, A)

Fig. 9 :

 9 Fig. 9: XRD diagrams of the powders obtained by the microwave assisted polyol

Fig. 10 :

 10 Fig. 10: SEM images of the powders obtained with microwave assistance with DEG and

Intens

  Figure 1

  Figure 6

Table 1 :

 1 Specific surface area according to the BET method of the precursors obtained by the classical or the microwave assisted processes with EG or DEG and flash heat treated at 500°C for 5min.

	Sample	Process	Solvent	S BET (m².g -1 )
	P DEG	polyol	DEG	24.6 ± 1.2
	M DEG	Microwave assisted	DEG	36.0 ± 1.8
	M EG	Microwave assisted	EG	23.3 ± 1.2

Acknowledgments

We would like to acknowledge the Ministère de l'Enseignement Supérieur et de la Recherche Scientifique of the Tunisian Republic and the Ecole Doctorale Matières, Molécules et Matériaux en Pays de Loire (3MPL) (ED 500) for their financial support.

The authors also express their thanks to Ms. Melanie Joly from the IUT of Le Mans for her help with BET measurements.


A.-L Renon

A Gentes
email: annie.gentes@telecom-paristech.fr

J Bobroff
email: julien.bobroff@u-psud.fr

Keywords: Design Theory, Design Education, Pluridisciplinarity, Material Agency, Aesthetic Formation

 to explain metamorphoses from the brief to the final realizations.

Literature Review

The literature on sciences and design shows numerous collaborative programs [START_REF] Cross | Science and design methodology: a review[END_REF][START_REF] Cross | Designerly ways of knowing: Design discipline versus design science[END_REF][START_REF] Bruffee | Collaborative learning: Higher education, interdependence, and the authority of knowledge[END_REF][START_REF] Stahl | Group Cognition: Computer Support for Building Collaborative Knowledge (Acting with Technology)[END_REF][START_REF] Renon | Observation, expérimentation, conception. La place du format dans la production des images scientifiques[END_REF][START_REF] Renon | Design and Aesthetics in Practices of Science[END_REF]. While interdisciplinarity is advocated by educational institutions and sustained by the analysis of professional design practices [START_REF] Gentes | Arts et sciences du design : la place des sciences humaines[END_REF] many students who are introduced to design multidisciplinarity are afraid of the vast array of disciplines that they should know and use. The question is how to train for an almost infinite set of knowledges? Is it even possible to do so or is it a myth? And how are students prepared to raise up to the challenge of not understanding the depth of other disciplines that they must work with? Some programs actually engage the students into scientific literacy with the usual argumentation as reported by [START_REF] Feinstein | Salvaging science literacy[END_REF]: sciences are helpful even for students who do not intend to engage into a scientific career because they are part of a general education [START_REF] Donnelly | Blended problem-based learning for teacher education: lessons learnt[END_REF]. Sciences are therefore part of a cultural heritage considered the literacy of contemporary humanists. Science literacy is also supposed to help people make better reasoning and therefore helps them better manage their lives. As far as design education is concerned, [START_REF] Findeli | Rethinking design education for the 21st century: Theoretical, methodological, and ethical discussion[END_REF] points out that design has been considered as an applied science. However, he remarks the impossibility of listing the infinite number of sciences that could be applied by design. Yet design also builds a relation to other sciences. In a first fieldwork (2016), we studied a case of education where disciplines, that at first sight have nothing in common, were brought together. We wanted to better understand how design uses interdisciplinarity in a designerly way to produce new objects [START_REF] Gentes | Arts et sciences du design : la place des sciences humaines[END_REF][START_REF] Tovey | Design pedagogy: Developments in art and design education[END_REF]. The analysis showed that interdisciplinarity in design can be better understood if one looks at the properties of these situations and how they actively support invention. Five properties that framed the interdisciplinarity of design were discovered and analyzed: affective, cognitive, reflexive learning, economics, and political (Gentes, Renon & Bobroff, 2016). Elaborating on this research, we wanted to further understand interdisciplinarity in practice through the observation of material transformations during the design work. To do so, we used some of the methods and concepts of the Actor Network Theory (ANT) so as to pay special attention to the non-human actors that structure the designers' work. After presenting how we used the ANT and its methods, we describe the transformations at play through two use cases in detail. The analysis shows three operations that seem to be key to understanding the design practice: translation, composition, and stabilization. We suggest to call these operations: "aesthetic formations" so as to emphasize the aesthetics at play in the design work. In the discussion, we suggest that these "formations" are supported by a theory of material agency (Knappett & Malafouris, 2008;[START_REF] Renon | Design and Aesthetics in Practices of Science[END_REF]) that we will try to develop after so and so.

Research Methods

Chain of transformations and Collaborative programs in Design & Science

The Actor-network Theory studies societies as collectives or networks [START_REF] Latour | On actor-network theory: A few clarifications[END_REF][START_REF] Latour | Reassembling the social: An introduction to actor-network-theory[END_REF] constituted by human and non-human actors in interaction. This theory takes into account objects and discourses, and the set of relationships and mediations that connects them. These relations are based on a series of translations or chains of transformations, which eventually constitute "the social". In the same way, the scientific fact is the result of a chain of transformations (instruments, articles, laboratory materials, subsidies, etc.) ANT tends to construe translation as a collaborative performance. Translation, by this account, is a communicative process in which actors inhabiting different social worlds enter into relations with each other, and begin to recast or reconstruct themselves, their interests and their worlds. The sociology of translation "takes the semiotic insight, that of the relationality of entities, the notion that they are produced in relations,and applies this ruthlessly to all materialsand not simply to those that are linguistic" [START_REF] Law | After ANT: complexity, naming and topology[END_REF]. Such relationships are not essential or given: they have to be made and maintained, or 'performed'. [START_REF] Law | Actor network theory and material semiotics[END_REF] emphasized the openness, uncertainty and revisability of ANT-inspired Studies. He suggests that we talk of « materiel semiotics » rather than ANT. Elaborating on Law, Yaneva (2015) illustrated the potentials of an Actor-Network Theory (ANT) perspective to design, arguing that design triggers specific ways of enacting the social, understanding design's investigation as a type of connector, not as a separate cold domain of material relations. Rather than mobilizing the ANT as a strict theoretical framework, we propose, following [START_REF] Law | Actor network theory and material semiotics[END_REF][START_REF] Fenwick | Actor-network theory in education[END_REF]), and Fenwick (2011), to take ANT into account both as a tool for reflecting the interactions between humans and nonhumans, understood as spaces of transformation, and to analyze these transformation spaces by re-situating the materiality inherent in any production of design [START_REF] Danholt | The translation by Design of Actor network theory (ANT)[END_REF].

IASDR 2017, Cincinnati, 31oct-3nov

Case study: an education program between design and physics Since 2011, François Azambourg and Julien Bobroff have been organizing workshops called "Design and Research" for students of a school of design in Paris, ENSCI les Ateliers. The workshops investigate forms and materials in a design project. Fifteen to twenty design students at different stages of the design curriculum but with no specific qualification in science have attended these workshops. The workshop lasts four months. In addition to informal interactions, there are generally six formal presentations. The students also have a permanent co-working space to develop their projects. During the workshops, students are given outreach seminars by the physicist together with physics lab visits and open discussions about physics. Students are then asked to conceive a design project inspired by the scientific material. The challenge of the workshop is to work on tangible productions while starting from intangible concepts and notions from fundamental physics. Each year, the designers and the physicist choose a new theme: "Supraconductivity" in 2011, "Quantum physics" in 2013, and "Light and optics" in 2014. Productions are evaluated at the end of the workshop during a collective presentation and exhibition. They are also displayed on websites and further used in various outreach activities: exhibits in science museums, outreach talks, science fairs… In the spring of 2016, the workshop "Design and Research" was sub-titled: "Voir l' invisible" ("Catching the invisible"). Anne-Lyse Renon made an ethnographic observation during the four month of the workshop (March to June 2016), collecting 12 hours of video, 562 pictures and interviews and informal discussions. Out of the 13 projects done by the students in this session, we selected mainly two (A and B) for this paper so as to give a detailed analysis of productions and discourses. A proposed a game for children and B a pastry cosmology. C is also mentioned who designed a book for children. We chose to focus mainly on students A and B because they presented interesting differences in terms of production (A a tool, B a tangible typology), and were positively evaluated in terms of originality and seriousness of the design work by the designer and the scientist.

Workshops: description of inputs and transformations

Asking design students to work with fundamental physics seems like a particularly tough pedagogical and design challenge. This section looks at how tangible objects were produced while addressing fundamental physics, intangible by essence.

The physicist was the first to suggest a way to solve the paradox. While the subject title could very well be interpreted in mystical terms, the introductory lesson delimited the scope of the project by using a vocabulary coming from physics: "What does « see » mean at the atomic scale? How do we capture and manipulate phenomena at the Nano scale?" He emphasized the scientific standpoint by mentioning:

human sight as well as the definition of "invisibility": the definitions were taken from biology and physics; tools: microscopes including the history of the instruments; recent scientific questions: the limitation of traditional microscopy (Richard Feynman) as well as the technical specificities of contemporary quantum microscopes.

Mostly, his presentation resolved the paradox of "Seeing the Invisible" through a history of IASDR 2017, Cincinnati, 31oct-3nov

science. However, this resolution was not presented as the only way to address the paradox.

The physicist and designers insisted that students would not be evaluated on their expertise in physics, yet they had to produce their own interpretation of what was at stake in the "invisible" within "the specificities of their own materials" (Designer François Azambourg).

The first lesson was followed by a session where students could manipulate scientific tools: magnifying glasses, lenses, mirrors, two or three traditional microscopes, small USB microscopes (which were connected to the computer), polarizers, flashlight, UV lamp and laser (e.g. Figure 1 & 2). strategies and heterogeneous materials. At first sight, it seems that none of the students were interested by the same things. However, at this stage of "exploration", we could observe two main postures: either, they isolated and circumscribed an artefact or a theme from the scientific world. Or, an artefact or a theme was the pretext to reach out to other worlds. For instance, student A used the session of manipulation as a stepping stone for her research since it was an occasion to identify tools and functions of microscopy, while student B chose the table of Mendeleev: "guided by the physician, I discovered the Mendeleev periodic table of the elements". For him, the starting point was more about building a taxonomy of matters than working about an optical phenomenon. B: "It was from there, on the confusion of the reigns, that I wanted to work, that is to say finally that in the aspect of the table of Mendeleev there is this confusion there since all the atoms create the infinite bodies of materials that are known " Questioned about their choices, the two students evoked (A) childhood memories of playing with tools and exploring, or (B) their personal attraction for the sensuality and plasticity of matters. The starting point of their design work already put together science and personal experience: A chose a scenario of use where people would manipulate microscopes, and B focused on blending the elements of the classification table.

A: "(...) I went (with a pedagogical association) (...) to La Cité des Sciences (The City of Sciences in Paris), and there I said "yeah, there you really have to do something for children, to play, etc."

Students also tried to find other connections and sources of inspiration through "autobrainstorming" (student A). For instance, very early on, student B compared the table of Mendeleev to Indian ritualistic objects and this comparison later led him to introduce the notion of "activation". The first version of his project therefore changed in contact with another network of references. Student A remembered treasure hunts, "hiding things" that she loved doing as a kid. She compared it to more recent experiences with kids at La Cité des Sciences (a place devoted to sciences) and this helped her do her auto-brainstorming. Another student, C, mentioned science-fiction literature that she had read. She also questioned students doing their PhD in Sci-Fi to get more visual and narrative references. This literary design space conforted her into doing a book for children.

This practice of associations is completed by another type of activities that starts from materials and gestures. Student B expressed a pronounced taste for the manipulation of materials. He mentioned that he had a habit of collecting things with which he experimented. Materials were for him at the basis of design experimentations: "To start with, I wanted to invent an elementary paste. So, really from a design point of view, how we could actually recreate an assembly of materials that would be in the form of micro elements ... type of powder, etc. So things one can combine with a more or less equivalent granulometry and which together, depending on the mixtures used, can constitute a number of very different properties ". He investigates even further the principles of combination, by imagining a moving plasticity of materials: "I think my idea was to make something that could be in constant evolution, hence alive. "

A found not only a tool but a good material to investigate: the project "Foldscope". Designed IASDR 2017, Cincinnati, 31oct-3nov

by Manu Prakash & Jim Cybulski in 2012, it is an open source microscope made of paper, downloadable in pdf, and hand-assembled with the addition of an optical lens). " I just wanted to see how it works, and understand how to build it." From there, she began an inquiry about optics and printed images, going successively from digital to analogical production of images in order to find a good way to change the scales of the details she wanted to show (e.g. Figure 3). B wanted to embody complex notions in a device as simple and obvious as possible. But more importantly, he wanted to design for the senses so as to share his interest for physical experience with matter. He finally decided to explore taste because of the subjective and intimate as well as intensely physical experience. He chose food as a fieldwork to investigate: "This was the trigger: I told myself that in fact the food world was very interesting because there is all this faculty of mixing, food, ingredients to create different types of food with different ... tastes, textures. It was hyper global and at the same time hyper simple of apprehension since it was enough to eat it to understand. So it was from there that I said to IASDR 2017, Cincinnati, 31oct-3nov myself I will explain chemical links by making people eat them".

The tangible qualities were essential to build new "versions" [START_REF] Béjean | Looking through tools and situations: organizing exploration in artistic practice[END_REF] to answer the initial paradox. The design work consisted in finding material configurations by comparing properties, testing physical limits, and matching gestures with materials. Materials fought back and stopped the experimentations because of their own properties, their "requiredness" [START_REF] Rosenthal | Sens et temps de la Gestalt[END_REF][START_REF] Potter | What is a designer: things, places, messages[END_REF]. The designers were surprised by the results that could be different from what they planned.

For example, through his use of materials B wished to change both the relation to a cooking recipe and the symbolic representation of the periodic classification (e.g. Figure 4). However, the implementation of the project was not without certain pitfalls, especially in the assembly of the elements, conditioned by their chemical composition and the properties adjoining their materiality. Hence, B selected 5 substances, which he tried to combine according to an experimental protocol. Since this assembly was not possible from one material to another, the productions finally presented were dictated by the possibilities and the resistances of the material. In the interview, B pointed out the "surprising combinations" of all natural elements and at the same time stressed that the " chemical compositions [of these elements] are much closer than what first appears".

Figure 4. the student B "pasty cosmology" as it was displayed at the final presentation, the cakes were tasted arranged in the Mendeleev table used as a tray.

For student B, the analogy with cooking goes beyond the mere pretext of production. From a chemical composition at the very beginning, he changes to an aesthetic composition.

The potentially infinite process of associations and configurations taking place at different moments was brought to a halt by the necessity of communication of the projects in formal presentations. We observe three stages of successive stabilization in the formation of composition: a first stabilization which is made by the choice of materials and their manipulation. Then from the relation between material properties and manipulation emerges an aesthetic stabilization, linked with the objective of a project rendering and the necessity of doing selections. And finally, the need for circulation leads to a final phase of stabilization which is a communication stabilization.

These presentations forced the students to choose a particular version of their project and to justify their choices. A went straight to a game and emphasized her scenario of use: to provide a microscope that would be a game for kids. The sobriety of manufacture she shaped found its origin in the will of student A to lead the project to an economy of means. The implementation of this playful microscope has thus taken a turn of popularization in the perspective of its concreteness, and the simplicity of its manufacture (e.g. Figure 5). Conversely, student B proposed to develop a "culinary nomenclature", in order to explore the complexity of variations and assemblages of edible matter in the manner of atomic transformations (e.g. Figure 6). His quote from Carl Sagan "If you want to make an apple pie from scratch, you must first create the universe." in some way contributed to the network of associations that creates the "Pastry Cosmology".

IASDR 2017, Cincinnati, 31oct-3nov

Discussion

From the outset of the workshop, the students took (i) the lack knowledge and (ii) the notion of invisible, as a constraint of production. Two strategies emerged to tackle the paradox of "seeing the invisible".

Student A wanted to produce a popularization environment. Her idea was to take the scientific technical instrument (the microscope) and to explore the dimension of simulation, hence the tangible tool and the focus on its manipulation. This manipulation is made possible by the DIY construction process, which in turn simulates an appropriation of scientific and technical knowledge.

In the case of student B, the intuitively sought-for analogy between concepts in physics and their modalities of material transcription, proceeds from a symbolization. His work of transfer reveals a relation with the analogy of science to systems (Renon, 2015a;[START_REF] Renon | Design and Aesthetics in Practices of Science[END_REF]. This "aesthetics of systems" (Burnham & Haacke, 1968), which is dear to conceptual art and to the processes of the "artificial sciences" (Simon, 1969), consists in finding a grammatical or even syntactic relationship between materials in order to construct a universal language close to the periodic table. For student B, understanding the periodic table of Mendeleev relies on an iconic transposition, term by term, or rather terms to materials. And these translation and composition take place through the constraints of the materials themselves, and their specificities, from abstract physics notions to design material production.

However, as we looked at the dynamics of the design workshop, we observed "composites" (Le [START_REF] Le Marec | De l'étude des usages à une théorie des composites: objets, relations et normes en bibliothèque[END_REF] that included living and non-living actors, symbolic and tangible material, personal memories and inputs from other designers and physicist but also operations of transformation. Elaborating on the concept of composites as heterogeneous semiotic combinations, we observed how these combinations evolved all along the project but also changed initial meanings by cutting and relating elements in different ways.

The first "aesthetical formation" consisted of translating and networking operations.

Students mixed elements of physics presented at the beginning of the project with personal memories, associating different worlds of references. This propaedeutic moment activated a network of knowledge pre-configuring how they were going to orient themselves. The presentation of the subject was already tacitly a way of setting up chains of transformations towards a project space. However, the translation in this case is not retro-active as in the case of a scientific activity studied in STS. Each "translation" produces a new version and also, as Gentes and Bejean showed in the case of a theater production [START_REF] Gentes | Making Sense of Constellations of Objects: a Case Study of Computer-Aided Writing Practices in Theatrical Staging[END_REF], produces a new definition of the initial paradox. This aesthetical formation is therefore a chain of dynamic configurations where every element influences each other.

The second type of aesthetical formation consists in composing the "initial paradox" with tangible materials, as well as by gestures and the "manner" of each designer. While these were often chosen brought by the "translating" and "networking" formation, they also had their own logic and resisted the network, surprising their creator. These compositions were evolving because each material resisted, surprised not only by itself but new resistance and new material "behaviours" that appeared when they were brought together. The final video of student C is an illustration of this process of metamorphosis through composition (Figure. 7). This composing process which can be described as a field of tensions [START_REF] Gentes | The indiscipline of design: Bridging the gap between humanities and engineering[END_REF] sometimes reached a balance: what we suggest to call a stabilizing formation. Things seem to fall into place according to their authors. While most of the literature on design activity focuses on the fixation / defixation issue, we suggest that the design process can also be described as a quest for balance between heterogeneous elements. This balance between elements in tension fixes one version of the design work. Such states of stabilisation are obvious when students need to communicate about their projects during formal presentations. In that particular case, the stabilising formation is directly related to the necessity of social circulation of the project. However, it would be insufficient to attribute this stabilisation formation to the social circulation only. Students, and their supervisors, feel that a certain authenticity is achieved.

The videos that give a view of the work process are often a dramaturgy of this goal. The denouement is presented as a refined process of choice, an elimination of useless elements, and an equilibrium reached by the designed artifact.

Conclusion

In the framework that we analyzed, designers tapped into their personal history and experience of other projects -in effect introducing even more facts into the project -to create new representations at the crossroads of disciplines but also letting matter speaks for itself in IASDR 2017, Cincinnati, 31oct-3nov compositions and eventually stabilized forms ready for circulation. The radicality of the experiment that we presented here lies in the fact that fundamental physics is intangible in essence and the starting point of the design project is therefore abstract. However, the designers took into account and invested the scientific material, which became both a tool and a function for exploration. The word "material" here does not simply point to what is tangible in the productions, nor is defined by a subject / object dichotomy. It is made of iconic, technical and semiotic dimensions, which constitute the "material agency" inherent in any design process. For Malafouris, "while agency and intentionality may not be properties of things, they are not properties of humans either: they are the properties of material engagement, that is, of the grey zone where brain, body and culture conflate" (Knappett & Malafouris, 2008). For us material agency in design is a combination of material engagement as developed by Knappett & Malafouris and the continuous aesthetical dynamic formation process between abstraction, symbolization and shaping process [START_REF] Renon | Design and Aesthetics in Practices of Science[END_REF]. To address the abstraction, it is particularly obvious that the design students constructed their projects between gesture and materiality. By focusing on the students experience, the concept of material agency therefore emerged not only as a grey zone where people and matters are engaged together but also as a "zone" where aesthetic formations take place that are at the heart of the design activity.

Here we can extend the ANT perspective so as to explain the combination of non-knowledge and experience. Even if ANT has been used to explain the design process in recent years, we think that the chains of transformations in the design process cannot be compared strictly to the scientific process. In the ANT perspective, the chains of transformations, from the experiment to the results, are described as fundamentally reversible and reproducible. One can go from the results back to the first observations et redo the experiments under the same conditions of reproducibility. But in a design process, the material agency includes the personal expression that is based in the networking practice of the designer and the resistance of materials while they are composed: shapes and matters talk back. The whole process is eventually not reversible because each "stage" transforms the meaning of the previous "composite" made of operations and matters. We therefore suggested to use the expression "aesthetical formations" so that we could represent the different qualities of these situated practices. First, we could see that they were part of a learning and appropriation process. Formation is here understood as "expansive learning". The active form of the word "formation" also points to the fact that the design process is potentially an infinite semiotic process. In their evocation of the design process, students deployed an encyclopaedic network of associations. The situations eventually stabilized into certain combinations where they could finally circulate, triggering special emotions and experiences. We also qualified these formation as "aesthetical". By that we wanted to reassert not only a personal, subjective experience but also as a cultural and historical situation, as well as a social space of communication.

Figure 1 .

 1 Figure 1. The physicist manipulating an optic refraction artefact and doing a demonstration to the student with the designer teacher on his left.

Figure 2 .

 2 Figure 2. Students experimenting the different instruments and optical lenses and microscopes brought by the physicist

Figure 3 .

 3 Figure 3. Student A handling different type of photographic films, comparing the transparency, the sharpness and the possibility to change the scale.

Figure 5 .

 5 Figure 5. Display of the evolution from the original paper microscope (on the left ) to the A first prototype including a new shape and a game .

Figure 6 .

 6 Figure 6. Detail of one of the combination for H2O, using biscuit for Hydrogen, and chocolate for Oxygen

Figure 7 .

 7 Figure 7. Screenshots of the process described by Student C, from the first approach of the project till the final realisation.