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Conference Paper
Sulim, O., R. Ribeiro, I. Esteves, C. Antunes, A. Garate, P. Duarte, I. Ferreira, J. Mota, and M. Plaza, Design of structured adsorbents for aplications in gas adsorption processes - Conventional shaping vs 3D-Printed formulation, , 5-10 March, 2017. Abstract

Microporous materials highly activated and with potential to be used as adsorbents in many applications for gas
separation/purification are usually available as powders. These solids usually have a great and reversible gas
uptake, high gas selectivity, good chemical and thermal stability, but are unsuitable to be used in gas adsorption
processes, such as Pressure Swing Adsorption (PSA) or Simulated Moving Bed (SMB).
Zeolites, carbons and more recently metal-organic frameworks (MOFs) are examples of those materials. Their
use in adsorption-based processes are dependent of their upgrading from powders (micrometer scale) to
particles (pellets, spheres or granules at millimeter scale). This would overcome large pressure drops and
consequent energy consumptions when packing adsorbent columns in those processes. Thus, shaping
adsorbents is an important step to use them in industry, although it greatly affects their capacity and selectivity
towards a specific gas separation.
In this work, we explore techniques to shape powdered adsorbents, followed by their textural and mechanical
characterizations, and the study of their adsorption properties towards the main components of post-combustion
flues gases (CO2 and N2). Materials densification is proposed by employing two approaches:
- Conventional shaping through binderless mechanical compression and binder-containing extrusion; and
- Formulation by 3D printing (or additive manufacturing) to produce packed bed morphologies that
precisely replicate computer aided design (CAD) models.
Porous separation media are important for fluid-solid contacting in many unit operations, including adsorption.
Due to practical limitations, media particles are typically packed randomly into a column in a shaped form,
allowing fluid to flow through the interstitial voids. Key to the effectiveness of packed columns are the flowrelated properties of mass transfer, fluid distribution and dispersion, and back pressure, which in turn depend
upon packing geometry. Until now, no alternative was found to overcome this limitation and have optimal
ordered packing arrangements at the micron scale. 3D-Printing (or additive manufacturing) brings a wide range
of benefits that traditional methods of manufacturing or prototyping simply cannot. With this approach, complex
ordered geometries, that are not possible by conventional extrusion, can be designed and printed for a porous
media, being the equipment resolution the only limiting step to overcome.
The effect of parameters like compression force, particle sieving, binder nature, binder/adsorbent ratio were
firstly studied using conventional shaping techniques, as a basis for the consequent development of 3D-printed
formulations. The structured samples are then characterized and adsorption equilibria studies are performed on
them to evaluate their performance as media for gas adsorption separation processes. A volumetric/manometric
adsorption unit built in-house was used for this purpose. Relevant experimental data is obtained, which allows to
conclude that 3D-printed media can be an alternative porous media for application in gas adsorption processes.

Bari, M., J. Loureiro, M. Pudas, K. Tappura, K. Jaakola, M. Ruoho, I. Tittonen, S. Volz, C. Pavan, K. Costabello, D. Bollen, M. Haslam, and I. Ferreira, "TransFlexTeg: Large area transparent thin film thermoelectric devices for smart window and flexible applications", 14th European Conference on Thermoelectrics, ECT 2016, 20-23 Sep, 2016. Abstract

The main objective of TransFlexTeg is to develop an innovative large area distributed sensor network integrating transparent thin film thermoelectric devices and sensors for multifunctional smart windows and flexible high impact volume applications. Different breakthrough concepts will be developed: 1) large area high performance transparent thermoelectric thin films deposited on flexible substrates for thermal energy harvesting; 2) low cost high throughput thin film thermal sensors for thermal mapping and gesture sensing; 3) flexible smart windows and walls with energy harvesting, environmental sensing and wireless communication functionalities. This technology aims to demonstrate the functionalities of a smart window able to measure air quality and environmental parameters such as temperature, sun radiation and humidity. The data is automatically collected and can be utilized for controlling heating, cooling and ventilation systems of indoors. Active radio interface enables long range communication and long term data collection with WiFi or a similar base station. The proposed concept of smart windows replaces several conventional sensors with a distributed sensor network that is integrated invisibly into windows. In addition to the power generated from the thermal energy harvesting, the thermoelectric elements (TE) are also used as temperature sensors that, while being distributed over large area, enable thermal mapping of the area instead of just one or a few values measured from particular points. This smart window can be produced on glass. The active layer itself can be flexible glass layer or polymer sheet, which will significantly broaden the field of applications and improve business opportunities. Both can be manufactured in batch, or in Roll to Roll Atomic Layer Deposition (R2R ALD) process. High environmental impact is expected with savings of more than 25% of the electrical usage of residential homes and office buildings.

Journal Article
Mendes, D. N. D. L., A. Gaspar, I. Ferreira, J. P. B. Mota, and R. P. P. L. Ribeiro, "3D-printed hybrid zeolitic/carbonaceous electrically conductive adsorbent structures", Chemical Engineering Research and Design, vol. 174, pp. 442-453, 2021.
Neves, N., A. Lagoa, J. Calado, B. A. M. do Rego, E. Fortunato, R. Martins, and I. Ferreira, "Al-doped ZnO nanostructured powders by emulsion detonation synthesis – Improving materials for high quality sputtering targets manufacturing", J. Eur. Ceram. Soc., vol. 34, issue 10, pp. 2325-2338, 2014. AbstractDOI

Emulsion detonation synthesis method was used to produce undoped and Al-doped ZnO nanostructured powders (0.5–2.0 wt.% Al2O3). The synthesized powders present a controlled composition and a morphology which is independent on the doping level. The XRD results indicate wurtzite as the single phase for undoped ZnO and the presence of gahnite as secondary phase for Al-doped ZnO powders. The sintering behavior of each powder was studied based on their linear shrinkage and shrinkage rate curves, showing the high sinterability of the powders. Activation energies for densification in the earlier stage were calculated for all compositions and possible sintering mechanisms are suggested depending on the doping level. The high chemical homogeneity and sinterability and the lower electrical resistivity of the bulk Al-doped sintered samples demonstrates the feasibility of emulsion detonation synthesis for the production of high quality Al-doped ZnO powders to be used in ceramic sputtering targets manufacture.

Ropio, I., A. C. Baptista, J. P. Nobre, J. Correia, F. Belo, S. Taborda, M. B. M. Faustino, J. P. Borges, A. Kovalenko, and I. Ferreira, "Cellulose paper functionalised with polypyrrole and poly(3,4-ethylenedioxythiophene) for paper battery electrodes", Org Electron, 2018. AbstractDOI

A simple process of commercial paper functionalisation via in situ polymerisation of conductive polymers onto cellulose fibres was investigated and applied as electrodes in paper-based batteries. The functionalisation involved polypyrrole (PPy) and Poly (3,4-ethylenedioxythiophene) (PEDOT) as conductive polymers with the process of functionalisation optimised for each polymer individually with respect to oxidant-to-monomer ratios and polymerisation times and temperature. Paper with conductivity values of 44 mS/cm was obtained by exposing the samples to pyrrole vapour for a period of 30 min at room temperature; however, polymerisation at temperatures of 40 °C lead to higher conductivity values to up 141 mS/cm. Consequently, functionalised PPy and PEDOT papers were applied as cathodes in batteries with Al foil anodes and commercial paper soaked in an electrolyte solution of NaCl.

Baptista, A. C., I. Ropio, B. Romba, J. P. Nobre, C. Henriques, J. C. Silva, J. I. Martins, J. P. Borges, and I. Ferreira, "Cellulose-based electrospun fibers functionalized with polypyrrole and polyaniline for fully organic batteries", J Mater Chem A, vol. 6, issue 1, pp. 256-265, 2018. AbstractDOI

A novel cellulose-based bio-battery made of electrospun fibers activated by biological fluids has been developed. This work reports a new concept for a fully organic bio-battery that takes advantage of the high surface to volume ratio achieved by an electrospun matrix composed of sub-micrometric fibers that acts simultaneously as the separator and the support of the electrodes. Polymer composites of polypyrrole (PPy) and polyaniline (PANI) with cellulose acetate (CA) electrospun matrix were produced by in situ chemical oxidation of pyrrole and aniline on the CA fibers. The structure (CA/PPy|CA|CA/PANI) generated a power density of 1.7 mW g−1 in the presence of simulated biological fluids, which is a new and significant contribution to the domain of medical batteries and fully organic devices for biomedical applications.

Cristovão, A. F., D. Sousa, F. Silvestre, I. Ropio, A. Gaspar, C. Henriques, A. Velhinho, A. C. Baptista, M. Faustino, and I. Ferreira, "Customized tracheal design using 3D printing of a polymer hydrogel: influence of UV laser cross-linking on mechanical properties", 3D Print Med, vol. 5, pp. 12, 2019.
Soares, Í., J. Faria, A. Marques, I. A. C. Ribeiro, C. Baleizão, A. Bettencourt, I. Ferreira, and A. C. Baptista, "Drug Delivery from PCL/Chitosan Multilayer Coatings for Metallic Implants", ACS omega, vol. 7, pp. 23096-23106, 2022.
Loureiro, J., T. Mateus, S. Filonovich, M. Ferreira, J. Figueira, A. Rodrigues, B. F. Donovan, P. E. Hopkins, and I. Ferreira, "Hydrogenated nanocrystalline silicon thin films with promising thermoelectric properties", Appl. Phys. A, vol. 120, issue 4, pp. 1497–1502, 2015. AbstractDOI

The search for materials with suitable thermoelectric properties that are environmentally friendly and abundant led us to investigate p- and n-type hydrogenated nanocrystalline silicon (nc-Si:H) thin films, produced by plasma-enhanced chemical vapor deposition. The Seebeck coefficient and power factor were measured at room temperature showing optimized values of 512 µV K−1 and 3.6 × 10−5 W m−1 K−2, for p-type, and −188 µV K−1 and 2.2 × 10−4 W m−1 K−2, for n-type thin films. The thermoelectric output power of one nc-Si:H pair of both n- and p-type materials is ~91 µW per material cm3, for a thermal gradient of 8 K. The output voltage and current values show a linear dependence with the number of pairs interconnected in series and/or parallel and show good integration performance.

Loureiro, J., T. Mateus, S. Filonovich, M. Ferreira, J. Figueira, A. Rodrigues, B. F. Donovan, P. E. Hopkins, and I. Ferreira, "Improved thermoelectric properties of nanocrystalline hydrogenated silicon thin films by post-deposition thermal annealing", Thin Solid Films, vol. 642, pp. 276-280, 2017. AbstractDOI

The influence of post-deposition thermal annealing on the thermoelectric properties of n-and p-type nanocrystalline hydrogenated silicon thin films, deposited by plasma enhanced chemical vapour deposition, was studied in this work. The Power Factor of p-type films was improved from 7× 10− 5 to 4× 10− 4 W/(mK 2) as the annealing temperature, under vacuum, increased up to 400° C while for n-type films it has a minor influence. Optimized Seebeck coefficient values of 460 μV/K and− 320 μV/K were achieved for p-and n-type films, respectively, with crystalline size in the range of 10 nm, leading to remarkable low thermal conductivity values (< 10 Wm− 1. K− 1) at room temperature.