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The growth mechanism of Atomic Layer Deposition (ALD) on polymeric surfaces differs from growth on inorganic solid substrates, such as silicon wafer or glass. In this paper, we report the growth experiments of Al2O3 and ZnO on nonwoven poly-L-lactic acid (PLLA), polyethersulphone (PES) and cellulose acetate (CA) fibres. Material growth in both ALD and infiltration mode was studied. The structures were examined with a scanning electron microscope (SEM), scanning transmission electron microscope (STEM), attenuated total reflectance-fourier-transform infrared spectroscopy (ATR-FTIR) and 27Al nuclear magnetic resonance (NMR). Furthermore, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis were used to explore the effect of ALD deposition on the thermal properties of the CA polymer. According to the SEM, STEM and ATR-FTIR analysis, the growth of Al2O3 was more uniform than ZnO on each of the polymers studied. In addition, according to ATR-FTIR spectroscopy, the infiltration resulted in interactions between the polymers and the ALD precursors. Thermal analysis (TGA/DSC) revealed a slower depolymerization process and better thermal resistance upon heating both in ALD-coated and infiltrated fibres, more pronounced on the latter type of structures, as seen from smaller endothermic peaks on TA.

Electrospinning is a method that can be used in the production of polymeric nanofibres. Polymer solution is drawn into sub-µm to nanosized fibres utilizing electric field. The structure of electrospun web has intrinsic properties such as small fibre diameter, small pore size, and high specific surface area which are beneficial for various applications. In addition, fibres can be functionalized in various methods. Thin (nm scale), conformal coatings made by atomic layer deposition (ALD) can be used for functionalization. For example, metal oxides can provide interesting properties, such as electronic, antimicrobial, self-cleaning and hydrophobic properties among others, to fibrous materials. Combining electrospinning and thicker ALD layer enables also preparation of sub-µm tubes, if core fibres are removed. Aim of this work was to make electrospun fibres from three polymers, cellulose acetate (CA), polyether sulphone (PES) and poly-L-lactide (PLLA) to be used as substrates for ALD. In this presentation we will report preparation electrospun fibres using solvent mixtures, structure of electrospun sheets (PLLA shown as an example), and preliminary results of ALD carried out on electrospun sheets, as well as discuss the possibilities of ALD method in functionalization and processing of electrospun fibres.

Atomic layer deposition (ALD) is a layer-by-layer deposition process based on repeated self-limiting gas-solid reactions by using volatile precursors. It is suited for producing dense and pinhole-free inorganic nanoscale coatings uniform in thickness at relatively low temperatures. The purpose of this presentation is to demonstrate the potential and the challenges of using ALD to create functional coatings for polymer films. ALD is an efficient tool for improving the barrier properties of polymer films. However, adequate barrier properties are only one of the key requirements set for the packaging materials. As far as safety issues are concerned, these coatings, for example, seem not to fall under the European definition of nanotechnology and migration is low enough to meet the requirements set by current European regulations. ALD can also be used to create antimicrobial coatings, and thin oxide coatings can be modified for improved mechanical and surface properties. It is recommended that ALD coatings are protected with an additional polymer layer providing also heat sealability. Although ALD is today carried out in batch mode, the development of roll-to-roll processes will enhance the feasibility of ALD for e.g. packaging materials

Atomic layer deposition (ALD) is a surface controlled layer-by-layer process based on self-limiting gas-solid reactions. Thin films are prepared using volatile precursors in repeating cycles until a preferred film thickness is obtained. ALD is suited for producing dense and pinhole-free inorganic films uniform in thickness. Most important commercial applications lies today in microelectronics, but they range from displays to protective coatings on silver jewellery. The purpose of this presentation is to demonstrate both the potential and the challenges of using ALD to create thin barrier layers for packaging materials. ALD can have a profound effect on the barrier values of various polymer films and polymer coated paperboards. As far as safety issues are concerned, these thin barrier films seem not to fall under the European definition of nanotechnology and migration is low enough to meet the requirements set by current European regulations. ALD can also be used to create antimicrobial thin films, and thin oxide films can be modified for improved mechanical and surface properties. It is recommended that ALD deposited thin films are protected with an additional polymer layer also providing heat sealability. Although ALD is today carried out in batch mode, the development of roll-to-roll processes will enhance the techno-economic feasibility of ALD, among others, for packaging materials.

Electrospinning can be used to prepare submicron polymeric or composite fibres. Such fibres can be as precursors and subsequently pyrolysed into carbon fibres. The small fibre diameter, small pore size, and high surface area of the nanofibre web are properties that are advantageous for various applications including catalysis. In this study we prepare corrosion resistant and electrically conductive catalyst support structures utilizing electrospinning. In this presentation we present first results of the study carried out within project Catapult (novel CATAlyst structures employing Pt at Ultra Low and zero loadings for auTomotive MEAs; Supported by EU FCH-JU; Grant agreement no 325268). Our approach to produce core-shell carbon-ceramic catalyst supports include preparation of electrospun precursor fibres, stabilization and carbonization of precursor fibres into carbon, and atomic layer deposition (ALD) coating method to produce semi-conducting oxide layer onto carbon fibres. Electrospun fibre sheets are prepared from polyacrylonitrile (PAN) and mixture of PAN and carbon nanotubes (CNT) with lab scale electrospinning setup equipped with rotating drum collector in dry atmosphere. Stabilization and carbonization of web samples are carried out using tubular furnace suitable for roll-to-roll operation, and carbon samples are coated with niobium doped titanium oxide in ALD batch reactor. Conductivities of carbon fibres and ALD coated carbon fibres were around 5-20 S/cm.

The general requirements for PEM fuel cell catalyst support materials are high electronic conductivity, high specific surface area and high electrochemical and chemical stability. Current structures typically consist of Pt particles on carbon black support material, but the mass activity of these high surface area nanoparticulate catalysts is restrainer for a large-scale commercialization of PEM fuel cell for vehicles. Reduction of platinum content per vehicle and increase of mass activity are solutions paving the way for a larger utilization of the PEM fuel cells. New approach for automotive PEM fuel cell catalysts are being developed in project CATAPULT (novel CATAlyst structures employing Pt at Ultra Low and zero loadings for auTomotive MEAs; Funded by EC FP7, Fuel Cells and Hydrogen Joint Technology Initiative, grant agreement n°.325268). In this new approach platinum is deposited as an extremely thin layer on corrosion resistant supports of various morphologies including fibrous and tubular structures. VTT's approach is to produce two types of structures: core-shell carbon-ceramic sub-µm fibrous and ceramic sub-µm tubular catalyst supports utilizing atomic layer deposition (ALD) method on electrospun sub-µm fibres. Within this presentation we will present results of Nb-Ti-oxide coatings made, firstly, on carbonized sub-µm fibres in order to obtain core shell fibrous supports and, secondly, on sacrificial polymeric fibres in order to make tubular supports for platinum coating also made by ALD method. Support production and the properties of the support materials are presented, and deposition of Pt catalyst layer is discussed in this presentation.

Atomic layer deposition (ALD) is an efficient tool for improving the barrier properties of polymer films and polymer-coated papers/paperboards. However, adequate barrier properties are only one of the key requirements set for the packaging materials. Purpose of this paper is to present the safety aspects related to polymer films with a thin ALD grown Al2O3 layer. Several approaches were tested. Based on our analyses ALD grown Al2O3 thin layers do not fall under the European Commission's definition of nanomaterial, and thus the limitations set in the Commission Regulation (EU) No 10/2011 on plastic materials would not be valid in this case. Al2O3 is also accepted as an additive for plastics in contact with food. Abrasive testing of polymer films, although detrimental in several cases to the film itself, did not increase the number of airborne particles. Coated silicon wafer and oriented polymer films were also exposed to specific simulants and key material properties were followed. Finally, we also tested the films for migration, although overall migration from a similar thin film has been regarded extremely low. Our tests were based on the worst case scenario, where the thin inorganic layer is exposed directly to the simulant. The Al2O3 coated films were affected by the simulant exposure, but the degree of impact depended also on the base film. This could indicate different thin layer growth on different polymer films. As a conclusion, such ALD grown Al2O3 thin layers require additional protective layers acting also as a sealant layer.

Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are examples of self-assembly based on repeated cycles of self-limiting gas-solid reactions. The precursors are pulsed into a reactor alternately, separated by inert gas pulses. During a single cycle, only one molecular layer is deposited on the surface, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. These cycles are repeated until a layer with a specific thickness is achieved. Few materials are, however, ideal. During the early film growth precursors adsorb onto the surface and absorb into the near-surface regions depending both on the substrate and the deposition parameters. These precursors can react with the substrate affecting e.g. mechanical, barrier and surface properties. The deposited material starts then to form clusters leading to nonuniform early film growth. The purpose of this presentation is to demonstrate that thin and non-uniform layers can be used to tailor the surface characteristics of different substrates. For example, print quality (ink spreading and penetration) of inkjet printing on polymer films can be adjusted with metal oxide. Secondly, this can be used to control water penetration into porous nonwovens. Third example demonstrates how adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a novel hybrid layer based on lactic acid. As the amount of material to be deposited is small, this will help to increase the speed in ALD/MLD processes designed for moving webs.

The goal was to study polymer films and coated paperboard as base substrates for atomic layer deposition (ALD), to understand the parameters affecting layer growth and functional properties, to characterize thin layers, and to assess their safety and sustainability. Barrier properties of most polymer films studied were improved by Al2O3 thin layers. The relative improvement was the most significant with cellulose and polyester films, while certain plastic additives completely prevented thin layer growth. Polymer pre-coatings on fiber-webs have to be smooth and have good film forming properties. Layer growth starts by sorption of precursors onto and into the polymer surface followed by chemical reactions with the polar oxygen groups of the polymer and a possible formation of an interphase. This is followed by cluster formation and growth through clusters. The amount of oxide needed to cover the polymer depends on its' surface chemistry. Surface chemistry of polymer film has an impact on the layer growth and final functional properties. Polymer pretreatments prior to the ALD can be used to improve the barrier properties. Ozone can activate difficult surfaces, and the barrier properties can be adjusted by choosing the oxygen source. In addition, deposition temperature should be as high as possible. Mechanical properties of oxide layers were improved by combining thinner oxide and inorganic-organic hybrid layers into a nanolaminate. In addition, a contact between the oxide layers and the bacteria promoted antimicrobial activity. Uniform Al2O3 barrier layers do not seem to fall under the EU's definition of nanomaterial. Migration of Al2O3 to food simulants was low. However, ALD coated polymers require a top layer to protect the oxide layer from stresses, to prevent dissolution and to act as a sealant.

Atomic layer deposition (ALD) is an efficient tool for improving the barrier properties of polymer films and polymer-coated papers/paperboards. However, adequate barrier properties are only one of the requirements set for the packaging materials. The purpose here is to present the safety aspects related to polymer films with a thin ALD deposited oxide barrier layers, especially those with Al2O3. Several approaches for testing ALD material were utilized. Based on our analyses ALD grown uniform Al2O3 thin barrier layers do not fall under the European Commission's definition of nanomaterial and the related limitations in the Commission Regulation. Plastic food contact materials may also contain non-authorized substances provided that their migration to food do not exceed very low migration limit (0.01 mg/kg food) and they are not mutagenic, carcinogenic nor toxic for reproduction, or are in nanoform. However, functional barrier concept should not be used to separate food and nanomaterial. Meanwhile, U.S. Food and Drug Administration (FDA) has a more inclusive approach to identifying products of interest in context of nanotechnology including size and/or function. FDA does not categorically judge products containing nanomaterials to be inherently harmful. Al2O3 and organic compounds of interest, such as ethylene glycol and glycerol, are accepted in Europe as additives for plastics in contact with food. Likewise, in USA these are accepted as either as indirect additives used in food contact substances or generally regarded as safe. According to some producers AlOx coatings have also been approved in USA for indirect contact with food. In our experiments abrasive testing of polymer films, although detrimental in several cases to the film itself, did not increase the number of airborne particles. ALD Al2O3 deposited at 100 ºC onto silicon and commercial polymer films were also exposed to liquid food simulants while evaluating the change in surface and barrier properties. Finally, we also tested the films for migration, although overall migration from thin films has been previously regarded as extremely low. The Al2O3 coated films were affected by the simulant exposure, but the impact depended on the substrate material and the oxidizing precursor. This indicates different thin layer growth on different polymer films. As a conclusion, ALD grown Al2O3 thin layer requires an additional, for example, laminated or extrusion coated top layer to protect it from both mechanical and chemical stresses, to prevent migration to the food, and also to act as a sealant layer in food packaging.

ALD has a relatively well-established position as a mainstream coating method in many application areas, mainly due to good film conformality and possibility of nanoscale material modification. Typically ALD deposited oxide materials, such as Al2O3, have surface hydroxyl groups after deposition, contributing to hydrophilic properties. For example measured contact angle for ALD alumina is around 50-60º and as-deposited TiO2 has superhydrophilic properties, which decay soon after deposition to 70-80º. For this presentation, we prepared SiO2 samples by PEALD. According to TOF-ERDA measurements the amount of carbon and nitrogen impurities were relatively low, but hydrogen content increased at low deposition temperatures. Carbon content was below 0.1 at-% if deposition temperature was 200 ºC. Regardless of the deposition temperature hydrogen content remained surprisingly high, being around 10-12 at-%. Low deposition temperature resulted in low refractive indices, most probably due to high hydrogen content. Residual stresses were determined with surface profilometer Veeco Dektak and wafer curvature method using Stoney s equation. The magnitude of the stress of SiO2 was too small to measure accurately for the given samples; most likely it was some tens of MPa on the compressive side. Water contact angles for PEALD SiO2 were below 20º. These values remained practically the same even after few months storage in ambient air. The main contribution for low contact angle is expected to be the high hydrogen impurity content which increases film hydrophilicity.

Electrospinning can be used to prepare submicron polymeric or composite fibres. Such fibres can be as precursors and subsequently pyrolysed into carbon fibres. The small fibre diameter, small pore size, and high surface area of the nanofibre web are properties that are advantageous for various applications including catalysis. In this study we prepare corrosion resistant and electrically conductive catalyst support structures utilizing electrospinning. In this presentation we present first results of the study carried out within project Catapult (novel CATAlyst structures employing Pt at Ultra Low and zero loadings for auTomotive MEAs; Supported by EU FCH-JU; Grant agreement no 325268). Our approach to produce core-shell carbon-ceramic catalyst supports include preparation of electrospun precursor fibres, stabilization and carbonization of precursor fibres into carbon, and atomic layer deposition (ALD) coating method to produce semi-conducting oxide layer onto carbon fibres. Electrospun fibre sheets are prepared from polyacrylonitrile (PAN) and mixture of PAN and carbon nanotubes (CNT) with lab scale electrospinning setup equipped with rotating drum collector in dry atmosphere. Stabilization and carbonization of web samples are carried out using tubular furnace suitable for roll-to-roll operation, and carbon samples are coated with niobium doped titanium oxide in ALD batch reactor.

Trends towards sustainable light-weight packaging materials not interfering with the end-of-life or recycling schemes. Thin film deposition techniques presented as tools for applying functional layers at the nano-scale on different surfaces. Techniques, such as atomic layer deposition, provide possibilities to enhance the barrier properties of sensitive materials including papers, polymer films and coated papers and boards