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Solution-processed oxide thin films for electrochromic devices application
Publication . Viegas, Jaime Silveira; Branquinho, Rita; Carlos, Emanuel
Electrochromic (EC) devices allow to reversibly change their colour when a small voltage is
applied and can be used in buildings, satellites or airplanes. NiO and WO3 are two promising
electrochromic materials with great electrochromic properties. Once NiO is a cathodic and WO3
is an anodic EC material, it is beneficial to combine them in a complementary effect electro-
chromic window. The production techniques of both NiO and WO3 devices have been evolving
but are still expensive due to typical vacuum-based and high pressure production processes.
Therefore, it is highly important to find new low-cost methods that can allow to produce EC
films with good electrochromic properties. Solution combustion synthesis (SCS) is a simple
low-cost method and a possible alternative. In this work, NiO and WO3 films were produced
through SCS and deposited by spin coating. Once the film production was optimized, they
were structurally, optically and electrochemically characterized. NiO and WO3 films presented
a thickness of (195±6) nm and of (53±3) nm, respectively. Both films did not present long range
order and only NiO films presented a porous structure. WO3 and NiO films presented an iden-
tical optical modulation of 20%. Cyclic voltammetry measures revealed two oxidation and two
reduction peaks for NiO films and only one reduction peak for WO3. Finally, NiO and WO3 films
presented low operating voltages and coloration/bleaching times of (21±1)/(8±1) s and
(45±7)/ (46±4) s, respectively. The films exhibited a promising reversible electrochromic be-
haviour which can be employed in complementary effect electrochromic windows after process
optimization.
Research on sodium bicarbonate abrasive jet machining technology for post-processing treatments of 3D printed PEEK implant to achieve non-destructive deburring and enhancing cell adhesion
Publication . Jiang, Zhouyu; Oliveira, João Pedro; Zhang, Yuchen; Liu, Lei; Shen, Jiajia; Su, Wenhao; Jing, Zihui; Wang, Mingliang; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); KeAi Communications Co.
The non-destructive deburring and hydrophilic surface machining of 3D printed Polyetheretherketone (PEEK) implants surface is critical for post-processing production of the implants. A green sodium bicarbonate abrasive jet machining technology was proposed in this study, aiming to ensure low damage of implants surface while effectively deburring and creating a hydrophilic surface conducive to cell adhesion. By comparing the machining effects of sodium bicarbonate abrasive and other hard abrasives (alumina and glass bead) under various jet pressures and angles, it was confirmed that sodium bicarbonate abrasive jet machining technology could provide the low damage (Ra = 1.75∼3.73 μm), moderate machining rate (0.24∼2.26 mg/s), excellent deburring performance, and outstanding surface cleanliness. Based on the comparison of experimental data and finite element simulation results, the fluid characteristics of abrasive particle beam and the combined machining mechanism (compression and plowing effect) of sodium bicarbonate abrasive jet machining technology were determined. Based on the consistent crystal phase and high purity displayed in the characterization of recycled abrasives, the feasibility of the designed abrasive recycling procedure was confirmed. Moreover, the fluorescence staining results of the adherent cell proliferation experiments confirmed that the sodium bicarbonate abrasive jet machining technology could effectively promote cell adhesion and growth by providing the matte elongated scratch-like micro-texture for the PEEK implants surface. In the future, this technology could facilitate the development for post-processing treatments in 3D printed PEEK implants additive manufacturing process.
Ecofriendly Printed Wood-Based Honey-Gated Transistors for Artificial Synapse Emulation
Publication . Vieira, Douglas Henrique; Carlos, Emanuel; Ozório, Maíza Silva; Morais, Maria; Fortunato, Elvira; Alves, Neri; Martins, Rodrigo; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; John Wiley and Sons Inc.
Printed electronics have traditionally used substrates and materials derived from fuel-based or less abundant and toxic resources, raising environmental concerns. Wood as a substrate reduces processing steps and enables the integration of intelligent functionalities in wooden furniture, offering biodegradability, nontoxicity, and derivation from renewable sources. In this work, sustainably printed transistors using zinc oxide nanoparticles as the active layer and honey electrolyte on wood substrates are demonstrated as a promising approach to reduce the environmental footprint of electronics. Despite the substrate's high roughness, the transistor exhibits excellent performance for screen-printed devices, with low on-voltage of 0.32 ± 0.12 V and high Ion/Ioff of (2.4 ± 0.9) × 104. Further analysis of hysteresis in transfer curves under varying scan rates and sweep ranges reveals the device's ability to adjust memory windows and on-current. Notably, these devices successfully emulate synapses, exhibiting neural facilitation and plasticity, indicating a shift toward sustainable computing. The device's dynamic response to single and successive presynaptic pulses demonstrates its ability to adjust synaptic weight, transition from transient to persistent memory, and pulse width-, frequency-, voltage-, and number-dependent excitatory postsynaptic currents. The successful emulation of the learning–forgetting–relearning–forgetting process underscores the device's potential for use in sustainable high-performance neuromorphic systems.
Dual and sequential drug delivery systems with antimicrobial and bone regenerative therapeutic effects
Publication . Rodrigues, Miguel A.; Ferreira, Carla; Borges, João P.; Bernardes, Beatriz G.; Oliveira, Ana L.; Santos, José D.; Lopes, Maria A.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); RSC - Royal Society of Chemistry
Bone defect healing is often compromised by infections acquired during surgery, hindering regeneration. An effective solution should first prevent infection and then promote bone repair. Localised drug-delivery systems capable of dual and sequential release of antimicrobial and bone-regenerative agents represent a promising solution; however, precisely controlling this sequential release remains an unmet challenge. To address this issue, this study explores a novel approach by developing delivery systems based on either hollow or non-hollow porous bioceramics with an alginate hydrogel matrix, resulting in cutting-edge systems with a controlled, stage-specific release of antimicrobial and bone regenerative agents that meet the clinical needs. Gentamicin served as the antimicrobial agent, while raloxifene and/or alendronate represented hydrophobic and hydrophilic bone-regenerative agents. The systems were evaluated for release profiles, kinetic modelling, and the effects of lyophilisation and sterilisation (using ethylene oxide or supercritical CO2) on drug stability and release kinetics. The release followed a precise dual-sequential pattern: gentamicin was released over 2-3 weeks, followed by another 2-3 weeks of bone-regenerative agents. Kinetic model fitting showed that gentamicin release was driven mainly by diffusion (with or without hydrogel swelling), and raloxifene/alendronate release was dominated by a mixture of diffusion and polymeric matrix swelling/erosion. Lyophilisation and sterilisation preserved release profiles, though timeframes shifted slightly, with supercritical CO2 causing minimal delay. Gentamicin retained strong antimicrobial activity post-processing, confirming the system's potential for infection control and bone repair.
Unveiling the microstructure evolution and mechanical properties in a gas tungsten arc-welded Fe–Mn–Si–Cr–Ni shape memory alloy
Publication . Lopes, J. G.; Martins, D.; Zhang, K.; Li, B.; Wang, B.; Wang, X.; Schell, N.; Ghafoori, E.; Baptista, A. C.; Oliveira, J. P.; DEMI - Departamento de Engenharia Mecânica e Industrial; UNIDEMI - Unidade de Investigação e Desenvolvimento em Engenharia Mecânica e Industrial; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Springer
Fe–Mn–Si–Cr–Ni shape memory alloys (SMAs) are unique low-cost materials with shape memory properties that grant them the ability to be used in both functional and structural applications. Such SMAs are especially sought in the construction sector for the creation of new components and/or the reinforcement of damaged ones. In this study, a Fe–17Mn–5Si–10Cr–4Ni–1(V, C) wt% SMA was gas tungsten arc welded, with the objective to investigate the microstructure and mechanical performance changes occurring after welding. A comprehensive assessment of processing, microstructure and properties relationships was established combining microscopy (optical and electron), synchrotron X-ray diffraction, microhardness mapping and tensile testing including cycling assessment of the joint’s functional performance. It is shown that the present SMA has good weldability, with the joints reaching nearly 883 MPa at fracture strain of 23.6 ± 2.1%. Alongside this, several microstructure differences were encountered between the as-received and as-welded condition, including the formation of ferrite and Fe5Ni3Si2 P213 cubic precipitates amidst the fusion zone in the latter region. Graphical abstract: (Figure presented.)
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
Concurso para Atribuição do Estatuto e Financiamento de Laboratórios Associados (LA)
Número da atribuição
LA/P/0037/2020