Search

Inorganic small particles stemming from mineral extraction (i.e. mining waste) could be used as additive for road paving applications to improve bitumen mechanical properties. Such an approach is expected to increase bitumen life-cycle cutting costs connected to their preparation and to reduce environmental issues. Experiment: Bitumens containing various amounts (up to 10% w/w) of filler made of mining tailings fine powder were characterized by means of oscillatory rheometry focusing on the effect of the filler content, temperature and filler milling time.(i) Superior resistance to stress, rutting, and fatigue were shown by the filler-containing mixtures. In addition, higher durability was observed for the filler concentration of 10% w/w. These effects were interpreted on the grounds of the physico-chemical interactions between the bitumen and the inorganic filler suggesting important utilizations. (ii) The present research points towards a circular economy path. Particularly, this study demonstrates how an abundant and potentially harmful waste can be converted into a high value-added component for road paving. Furthermore, increased durability of bitumen is beneficial in both economic and environmental terms.

Industrial effluents and wastewater treatment have been a mainstay of environmental preservation and remediation for the last decade. Silica nanoparticles (SiO2) obtained from rice husk (RH) are an alternative to producing low-cost adsorbent and agriculture waste recovery. One adsorption challenge is facilitating the adsorbate separation and reuse cycle from aqueous medium. Thus, the present work employs SiO2 supported on polylactic acid (PLA) nanofibers obtained by the electrospinning method for Rhodamine B (RhB) dye adsorption. The silica surface was modified with trimethylsilyl chloride (TMCS) to increase affinity towards organic compounds. As a result, the silanized surface of the silica from rice husk (RHSil) promoted an increase in dye adsorption attributed to the hydrophobic properties. The PLA fibers containing 40% SiO2 (w w−1) showed about 85–95% capacity adsorption. The pseudo-first-order kinetic model was demonstrated to be the best model for PLA:SiO2 RHSil nanocomposites, exhibiting a 1.2956 mg g−1 adsorption capacity and 0.01404 min−1 kinetic constant (k1) value. In the reuse assay, PLA:SiO2 membranes preserved their adsorption activity after three consecutive adsorption cycles, with a value superior to 60%. Therefore, PLA:SiO2 nanocomposites from agricultural waste are an alternative to “low-cost/low-end” treatments and can be used in traditional treatment systems to improve dye removal from contaminated waters.

A novel black organoammonium iodoplumbate semiconductor, namely phenyl viologen lead iodide C22H18N2(PbI3)2 (PhVPI), was successfully synthesized and characterized. This material showed physical and chemical properties suitable for photovoltaic applications. Indeed, low direct allowed band gap energy (Eg = 1.32 eV) and high thermal stability (up to at least 300 °C) compared to methylammonium lead iodide CH3NH3PbI3 (MAPI, Eg = 1.5 eV) render PhVPI potentially attractive for solar cell fabrication. The compound was extensively characterized by means of X-ray diffraction (performed on both powder and single crystals), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), UV-photoelectron spectroscopy (UPS), FT-IR spectroscopy, TG-DTA, and CHNS analysis. Reactivity towards water was monitored through X-ray powder diffraction carried out after prolonged immersion of the material in water at room temperature. Unlike its methyl ammonium counterpart, PhVPI proved to be unaffected by water exposure. The lack of reactivity towards water is to be attributed to the quaternary nature of the nitrogen atoms of the phenyl viologen units that prevents the formation of acid-base equilibria when in contact with water. On the other hand, PhVPI's thermal stability was evaluated by temperature-controlled powder XRD measurements following an hour-long isothermal treatment at 250 and 300 °C. In both cases no signs of decomposition could be detected. However, the compound melted incongruently at 332 °C producing, upon cooling, a mostly amorphous material. PhVPI was found to be slightly soluble in DMF (∼5 mM) and highly soluble in DMSO. Nevertheless, its solubility in DMF can be dramatically increased by adding an equimolar amount of DMSO. Therefore, phenyl viologen lead iodide can be amenable for the fabrication of solar devices by spin coating as actually done for MAPI-based cells. The crystal structure, determined by means of single crystal X-ray diffraction using synchrotron radiation, turned out to be triclinic and consequently differs from the prototypal perovskite structure. In fact, it comprises infinite double chains of corner-sharing PbI6 octahedra along the a-axis direction with phenyl viologen cations positioned between the columns. Finally, the present determination of PhVPI's electronic band structure achieved through UPS and UV-Vis DRS is instrumental in using the material for solar cells.

Carbon materials are well known for being a versatile class of materials able to transmit an electrical signal when used as fillers in composites. Among numerous carbon fillers, carbon nanotubes and graphene have been extensively investigated for the last thirty years. This paper compares graphene and carbon nanotube electrical (i.e., resistive and reactive) properties in the microwave range up to 3 GHz. The transmission and reflection parameters of both the microstrip transmission lines and patch antennas loaded with 33 wt.% of graphene and multiwalled carbon nanotubes (MWCNTs) were analyzed. Interestingly, for an identical composite matrix composition, different scattering parameters stemmed from the different morphology of the films, the diverse interactions between the graphene nanoplatelets, MWCNTs, and polymeric binders in conjunction with the intrinsic electrical characteristics of the two carbon materials.

Novel electrochromic (EC) materials were developed and formed by a two-step chemical deposition process. First, a self-assembled monolayer (SAM) of 2,2':6',2″-terpyridin-4'-ylphosphonic acid, L, was deposited on the surface of a nanostructured conductive indium-tin oxide (ITO) screen-printed support by simple submerging of the support into an aqueous solution of L. Further reaction of the SAM with Fe or Ru ions results in the formation of a monolayer of the redox-active metal complex covalently bound to the ITO support (Fe-L/ITO and Ru-L/ITO, respectively). These novel light-reflective EC materials demonstrate a high color difference, significant durability, and fast switching speed. The Fe-based material shows an excellent change of optical density and coloration efficiency. The results of thermogravimetric analysis suggest high thermal stability of the materials. Indeed, the EC characteristics do not change significantly after heating of Fe-L/ITO at 100 °C for 1 week, confirming the excellent stability and high EC reversibility. The proposed fabrication approach that utilizes interparticle porosity of the support and requires as low as a monolayer of EC active molecule benefits from the significant molecular economy when compared with traditional polymer-based EC devices and is significantly less time-consuming than layer-by-layer growth of coordination-based molecular assemblies.

Dye-sensitized solar cells (DSSCs) with photoanodes composed of chirality selected single-wall carbon nanotubes (SWNTs) have been fabricated and tested for first time. Single chirality SWCNTs separation (93% purity) have been achieved by modifying standard size exclusion gel chromatography. Chirality selection has allowed for “tuning” of the energy barrier at the TiO2/SWNT/FTO interface, electronic conductivity enhancement, and reduced SWCNTs-ruthenium dye competition for light absorption resulting in a 81% energy conversion efficiency improvement compared to mixed chirality cells. Unfortunately, energy conversion efficiency has been limited by cells’ low shunt resistance. Additionally, SWCNTs electron transfer properties have been exploited to prepare mixed and chirality specific CNTs based DSSCs’ counter electrodes.

A novel black organoammonium iodoplumbate semiconductor, namely phenyl viologen lead iodide C22H18N2(PbI3)2 (PhVPI), was successfully synthesized and characterized. This material showed physical and chemical properties suitable for photovoltaic applications. Indeed, low direct allowed band gap energy (Eg = 1.32 eV) and high thermal stability (up to at least 300 °C) compared to methylammonium lead iodide CH3NH3PbI3 (MAPI, Eg = 1.5 eV) render PhVPI potentially attractive for solar cell fabrication. The compound was extensively characterized by means of X-ray diffraction (performed on both powder and single crystals), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), UV-photoelectron spectroscopy (UPS), FT-IR spectroscopy, TG-DTA, and CHNS analysis. Reactivity towards water was monitored through X-ray powder diffraction carried out after prolonged immersion of the material in water at room temperature. Unlike its methyl ammonium counterpart, PhVPI proved to be unaffected by water exposure. The lack of reactivity towards water is to be attributed to the quaternary nature of the nitrogen atoms of the phenyl viologen units that prevents the formation of acid-base equilibria when in contact with water. On the other hand, PhVPI's thermal stability was evaluated by temperature-controlled powder XRD measurements following an hour-long isothermal treatment at 250 and 300 °C. In both cases no signs of decomposition could be detected. However, the compound melted incongruently at 332 °C producing, upon cooling, a mostly amorphous material. PhVPI was found to be slightly soluble in DMF (∼5 mM) and highly soluble in DMSO. Nevertheless, its solubility in DMF can be dramatically increased by adding an equimolar amount of DMSO. Therefore, phenyl viologen lead iodide can be amenable for the fabrication of solar devices by spin coating as actually done for MAPI-based cells. The crystal structure, determined by means of single crystal X-ray diffraction using synchrotron radiation, turned out to be triclinic and consequently differs from the prototypal perovskite structure. In fact, it comprises infinite double chains of corner-sharing PbI6 octahedra along the a-axis direction with phenyl viologen cations positioned between the columns. Finally, the present determination of PhVPI's electronic band structure achieved through UPS and UV-Vis DRS is instrumental in using the material for solar cells.

Gyroscopes are one of the next killer applications for the MEMS (Micro-Electro-Mechanical-Systems) sensors industry. Many mature applications have already been developed and produced in limited volumes for the automotive, consumer, industrial, medical, and military markets. Plenty of high-volume applications, over 100 million per year, have been calling for low-cost gyroscopes. Bulk silicon is a promising candidate for low-cost gyroscopes due to its large scale availability and maturity of its manufacturing industry. Nevertheless, it is not suitable for a real monolithic IC integration and requires a dedicated packaging. New designs are supposed to eliminate the need for magnets and metal case package, and allow for a real monolithic MEMS-IC (Integrated Circuit) electronic system. In addition, a drastic cost reduction could be achieved by utilizing off-the-shelf plastic packaging with lead frames for the final assembly. The present paper puts forward the design of a novel tri-axial gyroscope based on rotating comb-drives acting as both capacitive sensors and actuators. The comb-drives are comprised of a single monolithic moving component (rotor) and fixed parts (stators). The former is made out of different concentrated masses connected by curved silicon beams in order to decouple the motion signals. The sensor was devised to be fabricated through the PolyMUMPs&reg, process and it is intended for working in air in order to semplify the MEMS-IC monolithic integration.

The synthesis of hydroxylammonium lead iodide NH3OHPbI3 was accomplished by means of the reaction between water solutions of HI and NH2OH with PbI2 in sulfolane in conjunction with either crystallization by CH2Cl2 vapor diffusion or sulfolane extraction with toluene. The appropriate choice of the solvent was found to be crucial in order to attain the desired material. The synthesized compound was extensively characterized by single crystal and powder X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, FT-IR spectroscopy, 1H-NMR spectroscopy, TG-DTA-QMS EGA (Evolved Gas Analysis), ESI-MS, and CHNS analysis. NH3OHPbI3 is an extremely reactive, deliquescent solid that easily oxidizes in air releasing iodine. Furthermore, it is the first reported perovskite to melt (m.p. around 80 °C) before decomposing exothermally at 103 °C. Such a chemical behavior, together with its optical absorption properties (i.e. yellow-colored perovskite), renders this material totally unsuitable for photovoltaic applications. The deliquescence of the material is to be ascribed to the strong hydrophilicity of hydroxylammonium ion. On the other hand, the relatively high Brønsted acidity of hydroxylammonium (pKa = 5.97) compared to other ammonium cations, promotes the reduction of atmospheric oxygen to water and the NH3OHPbI3 oxidation. The crystal structure, determined by single crystal X-ray diffraction with synchrotron radiation, is orthorhombic, but differs from the prototypal perovskite structure. Indeed it comprises infinite chains of face-sharing PbI6 octahedra along the c-axis direction with hydroxylammonium cations positioned between the columns, forming layers on the ac plane. The solvent intercalates easily between the layers. The crystal structure is apparently anomalous considering that the expected Goldschmidt's tolerance factor for the system (0.909) lies in the range of a stable prototypal perovskite structure. Therefore, the strong hydrogen bond forming tendency of hydroxylamine is likely to account for the apparent structural anomaly.

We report on the rational design of a novel TiO2 based screen-printed material suitable for sensitive and selective detection of iron ions in water. This includes the synthesis and characterization of large mesoporous TiO2 nanostructures, screen-printing of thick titania films on glass surfaces and their functionalization with 2,2′:6′,2″-terpyridin-4′-ylphosphonic acid (terpy). The ultra-high affinity between iron ions and the TiO2-anchored terpy receptor makes this system potentially applicable to the analysis of iron in environmental, food, biological, and biomedical systems by a readily quantifiable colour change. Rapid (

Enactment and enforcement of international regulations restricting the use of lead-bearing solders has triggered plenty of research on Pb-free alloys for Integrated Circuits (ICs) packaging [1]. Nonetheless, Sn-Pb (63/37) eutectic still possesses unique features (e.g. low melting point, optimum mechanical properties, ideal surface tension allowing for holes and gaps wetting, capability of reducing, inhibiting or eliminating tin whiskers formation, etc.) hardly matched by lead-free solders. Alloys belonging to the SAC (Sn-Ag-Cu) category constitute the most widespread alternative to tin-lead solder because of their relatively low melting point [2], “composition-tunable” wettability [3], and high tensile strength (compared to the Sn-Pb eutectic). Particularly, SAC-305 (Sn = 96.5, Ag = 3, and Cu = 0.5 wt%) and SAC-405 (Sn = 95.5, Ag = 4, and Cu = 0.5 wt%) are by far the most employed solders compatible with the PTH (Plating Through Hole) layers connection method, the SMT (Surface Mounted Technology) components placement approach, and the surface finishes routinely used in PCBs manufacturing (e.g. organic solder preservative, lead-free hot air solder levelling, immersion silver, immersion tin, electroless nickel immersion gold, etc.). Furthermore, near eutectic SAC alloys (i.e. comprising 3-4 wt% of silver and 0.5-1 wt% of copper) also benefit from improved temperature cycling reliability mainly due to the high Ag content. The present work puts forward a new multi-layer electrodeposition technique amenable to wafer level chip scale package. By taking advantage of multiple Dynamic Liquid Drop/Meniscus (DLD/DLM), it is possible to plate binary, ternary and even quaternary solders at high-throughput, high precision and low cost [4]. The DLD/DLM exposes a constantly refreshed confined electrolyte volume in contact with the substrate surface [5]. The core of the method consists in interposing a rinse DLD/DLM into a sequential array of multiple independent electroplating DLD/DLMs (one for each component to deposited). Such a configuration results in a synergistic system composed of different plating outputs (plating head). Thereby, scanning the plating head over the wafer surface allows to coat the substrate with a thin layer of each component. Thus, each plating head pass leads to the deposition of a multilayered structure reflecting the targeted composition of the alloy. In other words, the current density is regulated in each DLD/DLM in order to obtain the desired wt% of every single component in the final solder deposit. Obviously, the total film thickness depends on the number of layers and can be varied in a wide range to allow an homogenous structures even without reflow. As a proof-of-concept, SAC-305 and SAC-405 bumps and caps on top of copper pillars [6] were deposited: 30 μm thick structures were electroplated through more than 350 layers of each element. Bumps as high as 10 µm (attained for net electroplating times as low as 14 seconds) were sectioned by FIB (Focused Ion Beam) to verify the agreement between the expected composition and the actual one. EDX analysis performed before and after reflow proved that the high number of layers produces a compositionally homogenous solder regardless of the metal deposition sequence and reflow temperature. A detailed investigation of SAC and quaternary SAC+Me (e.g. Ni, Zn) alloys composition will be presented (e.g. thermal, mechanical and wetting properties); EDX analysis before and after reflow proving that the high number of layers homogenous solder is obtained independently of metal deposition sequence and even without reflow. Furthermore, the nozzle sizes of the multiple DLD/DLM equipment will be correlated to the aspect ratio of the dry film opening. [1] A. Lancaster and M. Keswani, Integration, 75, 77 (2017). [2] A. B. Frazier, R. O. Warrington and C. Friedrich, IEEE Transactions on Industrial Electronics, 42(5), 423 (1995). [3] X. Xu, A. S. Gurav, P. M. Lessner and C. A. Randall, IEEE Transactions on Industrial Electronics, 58(7), 2636 (2011). [4] K. Kholostov, L. Serenelli, M. Izzi, M. Tucci, D. Bernardi, M.Balucani, IEEE Journal of Photovoltaics 5(2), 404 (2016). [5] M. Balucani, K. Kholostov, P. Nenzi, R. Crescenzi, D. Ciarniello, D. Bernardi, L. Serenelli, M. Izzi, M. Tucci,Energy Procedia, 43, 54 (2013). [6] K. Kholostov, A. Klyshko, D. Ciarniello, P. Nenzi, R. Pagliucci, R. Crescenzi, D. Bernardi and M. Balucani, 43, 2014 IEEE 64th Electronic Components and Technology Conference.

Radio-frequency identification (RFID) tags have been proposed as a low-cost item-level tracking system supplementing or replacing printed bar codes. Numerous applications are related to this technology. In this chapter, we present some of the novel solutions, based on nanostructured materials, used to improve the efficiency and flexibility of application of these devices.

The synthesis of hydroxylammonium lead iodide NH3OHPbI3 was accomplished by means of the reaction between water solutions of HI and NH2OH with PbI2 in sulfolane in conjunction with either crystallization by CH2Cl2 vapor diffusion or sulfolane extraction with toluene. The appropriate choice of the solvent was found to be crucial in order to attain the desired material. The synthesized compound was extensively characterized by single crystal and powder X-ray diffraction, UV-Vis diffuse reflectance spectroscopy, FT-IR spectroscopy, 1H-NMR spectroscopy, TG-DTA-QMS EGA (Evolved Gas Analysis), ESI-MS, and CHNS analysis. NH3OHPbI3 is an extremely reactive, deliquescent solid that easily oxidizes in air releasing iodine. Furthermore, it is the first reported perovskite to melt (m.p. around 80 °C) before decomposing exothermally at 103 °C. Such a chemical behavior, together with its optical absorption properties (i.e. yellow-colored perovskite), renders this material totally unsuitable for photovoltaic applications. The deliquescence of the material is to be ascribed to the strong hydrophilicity of hydroxylammonium ion. On the other hand, the relatively high Bronsted acidity of hydroxylammonium (pKa = 5.97) compared to other ammonium cations, promotes the reduction of atmospheric oxygen to water and the NH3OHPbI3 oxidation. The crystal structure, determined by single crystal X-ray diffraction with synchrotron radiation, is orthorhombic, but differs from the prototypal perovskite structure. Indeed it comprises infinite chains of face-sharing PbI6 octahedra along the c-axis direction with hydroxylammonium cations positioned between the columns, forming layers on the ac plane. The solvent intercalates easily between the layers. The crystal structure is apparently anomalous considering that the expected Goldschmidt's tolerance factor for the system (0.909) lies in the range of a stable prototypal perovskite structure. Therefore, the strong hydrogen bond forming tendency of hydroxylamine is likely to account for the apparent structural anomaly.

The response of materials to impinging electromagnetic waves is mainly determined by their dielectric (complex permittivity) and magnetic (complex permeability). In particular, radar absorbing materials are characterized by high complex permittivity (and eventually large values of magnetic permeability), Indeed, energy dissipation by dielectric relaxation and carrier conduction are principally responsible for diminishing microwave radiation reflection and transmission in non-magnetic materials. Therefore, the scientific and technological community has been investigating lightweight composites with high dielectric permittivity in order to improve the microwave absorption (i.e., radar cross-section reduction) in structural materials for the aerospace industry. Multiwalled carbon nanotubes films and their composites with different kind of polymeric resins are regarded as promising materials for radar absorbing applications because of their high permittivity. Nanocomposites based on commercial multi-wall carbon nano-tube (MWCNT) fillers dispersed in an epoxy resin matrix were fabricated. The morphology of the filler was analyzed by Field emission scanning electron microscopy (FESEM) and Raman spectroscopy, while the complex permittivity and the radiation reflection coefficient of the composites was measured in the radio frequency range. The reflection coefficient of a single-layer structure backed by a metallic plate was simulated based on the measured permittivity. Simulation achievements were compared to the measured reflection coefficient. Besides, the influence of morphological MWCNT parameters (i.e., aspect ratio and specific surface area) on the reflection coefficient was evaluated. Results verify that relatively low weight percent of MWCNTs are suitable for microwave absorption applications when incorporated into polymer matrixes (i.e., epoxy resin).

In this study, we present a range of efficient highly durable electrochromic materials that demonstrate excellent redox and lifetime stability, sufficient coloration contrast ratios, and the best-in-class electron-transfer constants. The materials were formed by anchoring as little as a monolayer of predefined iron complexes on a surface-enhanced conductive solid support. The thickness of the substrate was optimized to maximize the change in optical density. We demonstrate that even a slight change in molecular sterics and electronics results in materials with sufficiently different properties. Thus, minor changes in the ligand design give access to materials with a wide range of color variations, including green, purple, and brown. Moreover, ligand architecture dictates either orthogonal or parallel alignment of corresponding metal complexes on the surface due to mono- or bis-quaternization. We demonstrate that monoquaternization of the complexes during anchoring to the surface-bound template layer results in redshifts of the photoabsorption peak. The results of in-solution bis-methylation supported by density functional theory calculations show that the second quaternization may lead to an opposite blueshift (in comparison with monomethylated analogs), depending on the ligand electronics and the environmental change. It is shown that the variations of the photoabsorption peak position for different ligands upon attachment to the surface can be related to the calculated charge distribution and excitation-induced redistribution. Overall, the work demonstrates a well-defined method of electrochromic material color tuning via manipulation of sterics and electronics of terpyridine-based ligands.

Photovoltaics (PVs) market is currently dominated by mono- and multi-crystalline silicon, which has formed the basis of PV technology. However, breakthroughs in silicon solar cells photovoltaic energy conversion efficiency seem to be unlikely, and although further development in solar cells design might further increase their efficiency, cost projections are still not favorable. Hence, other materials and structures have been developed or are under development. In this chapter, we will examine different solutions, including thin film, heterojunction structures, organic materials, and hybrid (organic–inorganic) solar cells as possible alternatives to conventional crystalline PV devices. Furthermore, optoelectronic materials’ properties and solar cells configurations will be analyzed with respect to various PV applications.

While the plasmonic nature of graphene at terahertz frequencies has been widely reported, investigations on the practical utility of graphene at the microwave frequencies are sparse. In this paper, an ink comprising graphene thick films of different concentrations (12.5 wt.%, 25 wt.% and 33 wt.%) is prepared for deposition, by screen printing. Detailed investigation of the surface morphology of the films using SEM and AFM reveals that the graphene films present a homogeneous dispersion of the filler with a comparatively lower surface roughness at higher concentrations, and negligible agglomerates. The films are then printed in between copper electrodes on FR-4 substrate, commonly used in RF circuits, and the measured scattering parameters analyzed.

In recent years, low-cost carbons derived from recycled materials have been gaining attention for their potentials as filler in composites and in other applications. The electrical and mechanical properties of polymer composites can be tuned using different percentages and different kind of fillers: either low-cost (e.g., carbon black), ecofriendly (e.g., biochar), or sophisticated (e.g., carbon nanotubes). In this work, the mechanical and electrical behavior of composites with biochar and multiwall carbon nanotubes dispersed in epoxy resin are compared. Superior mechanical properties (ultimate tensile strength, strain at break) were noticed at low heat-treated biochar (concentrations 2–4 wt %). Furthermore, dielectric properties in the microwave range comparable to low carbon nanotubes loadings can be achieved by employing larger but manageable amounts of biochar (20 wt %), rending the production of composites for structural and functional application cost-effective.

Dynamic Liquid Drop/Dynamic Liquid Meniscus (DLD/DLM) is a patented technology suitable for localized chemical and electrochemical surface treatments. Indeed, DLD/DLM is an original and highly innovative tool able to continually renew the chemical solution used to produce selective chemical processes and treatments on a wide range of substrates and materials allowing very fast electrodeposition. High-speed electroplating is usually performed in the mass transport-controlled regime [1]. Therefore, the limiting current density (Jmax )is given by: Jmax=nFD/(δCb) Where D is the diffusion coefficient of the deposited species, n is the number of electrons per ion, F the Faraday constant, Cb the bulk concentration of the ions in the solution and δ the diffusion layer thickness. Under mass control conditions, metal ions are reduced as soon as they reach the electrode. Conversely, current densities higher than Jmax result into hydrogen evolution and lead to "burnt" and porous deposits [1]. Multiple approaches are employed to decrease the diffusion layer thickness (δ) and, therefore raise the limiting current density [2]: Improving the hydrodynamics (i.e. the flow velocity) of the electrolytic solution (e.g. jet plating, rotating electrode, ultrasonic agitation) Exploiting thermal effects stemming from Brownian motion and laser plating Modifying the electrodes’ current distribution through Pulse plating, and by tailoring the anode–cathode configuration Introducing additives into the electroplating bath formulation. Feasibility of copper electroplating with deposition rates as high as 50µm/s (corresponding to a 150A·cm-2 current density) have been proven by using laser jet-electroplating [3]. Furthermore, deposition rates of µm/s combined to high cathodic efficiency (e.g. > 80%) could be achieved through electrolyte flows in the m/s range[4]. The present work puts forward DLD/DLM systems, relying on special 3D nozzles, for two technologically-relevant electronics application: Mask-free metallization of HJT (i.e. Heterojunction) solar cells [5] by PRP (Pulse Reverse Plating) techniques. Electrolyte flow rates ranging from 0.1 to 2 m/s and electrodeposition rates between 1 and 5 µm/s can be attained (see figure 1.A). Deposition of highly uniform and homogeneous multicomponent alloys by taking advantage of sequentially arranged DLD/DLM plating heads (i.e. multilayer method). Lead-free solders (e.g. 305 and 405 SAC) were deposited at 0.8 micron/s from single-component electrochemical baths (see Figure 1.B) [6]. In addition, nanostructured composite materials comprised of multilayers containing up to 10-15% of nanoparticles can be fabricated by means of coalescent DLD/DLM (a variant of the original technique). Thus, new methods aiming at enhancing the performances of anti-corrosion coatings can be developed from the DLD/DLM. Furthermore, chemical treatments other than electrochemical deposition such as galvanic displacement and electroless coating can be easily implemented by the DLD/DLM approach. The presentation will provide a detailed description of the new sheet-to-sheet automatic DLD/DLM prototype equipment (see figure 1.C) with different 3D nozzles. Moreover, applications including a three-step metallization process for solar cells, multilayer deposition of two, three or four components lead-free solders, and nanostructured composites incorporating nanoparticles (e.g. SiO2 or Teflon). Finally, DLD/DLM capabilities in terms of speed of plating, flexibility and versatility will be also illustrated. In fact, the relatively small amounts of plating bath (typically 2-5 L) in conjunction with the possibility to adapt the technique to the coating of a broad range of surface areas (from tens of square microns to thousands of square centimeters) may bring about remarkable cost reductions in the electronic devices manufacturing and open a new route to electrodeposition. [1] F. C. Strong "Faraday's Laws in One Equation". Journal of Chemical Education. 38 (2) (1961) 98 [2] M. De Vogelaere, V. Sommer, H. Springborn, U. Michelsen-Mohammadein, "High-speed plating for electronic applications", Electrochimica Acta 47 (2001) pp. 109–116 [3] R. J. von Gutfeld and D. R. Vigliotti, "High-speed electroplating of copper using the laser jet technique" , Appl. Phys. Lett. 46, (1985), pp. 1003-1005 [4] L. J. J. Janssen "High-rate electrochemical copper deposition on bars" J. of Applied Electrochemistry 18 (1988) 339-346 [5] M. Balucani, S. Quaranta "A Breakthrough in Plating for Solar Cell Metallization" AiMES 2018, Tuesday, 2 October 2018: 14:40 Abstract MA2018-02 818 [6] M. Balucani, S. Quaranta "A Breakthrough in Pb-Free Solder Electroplating" AiMES 2018, Tuesday, 2 October 2018: 10:40 Abstract MA2018-02 1128 Figure 1

Electrochromic (EC) materials are a class of “smart” materials that change their optical properties in response to an applied potential. This optical change can be the development, loss, or variation in the color of the material. EC materials have recently become a research focus because of their high commercial applicability in “smart” windows, antiglare mirrors, and low-power displays. Most current EC materials are based on thick layers of EC molecules or EC molecules/ conductive polymer blends on the electrodes. The device properties depends strongly on the overall composition and distribution of the EC species in the polymer structure. We have developed an EC systems that contain as little as a monolayer of the EC molecules deposited onto a surface-enhanced conductive support [1]. The process involves the covalent attachment of various terpyridine-based ligand to the surface of a nanostructured conductive indium − tin oxide (ITO) screen-printed support by a simple submerging of the support into an aqueous solution of L. Subsequent reaction of with metal ions (e.g. Fe, Ru) leads to the formation the monolayer of the redox-active metal complex covalently bound to the ITO support. In addition, isolated and well-defined terpyridine- based metal complexes (Fe, Os,Co) were simply deposited on ITO screen-printed surface via conventional chlorobenzylsiloxane-based template. Our fabrication approach utilizes the inter-particle porosity of the support and requires as low as a monolayer of EC active molecule, giving significant molecular economy when compared with traditional polymer-based EC devices. This presentation will feature an overview of our synthetic methods, including how we can alter the color of the films by changing either the metal center of the ligand itself [2]. Spectro-electrochemical studies enabled us to correlation optical density with redox site density. Furthermore, detailed electrochemical studies enabled the determination of the kinetic rate constants for electron transfer for these films [3], which were considerably higher than other approaches in the literature. These novel light-reflective EC materials demonstrate a high color difference, significant durability, fast switching speed, excellent stability and high EC reversibility. References [1] J.T.S. Allan, S. Quaranta, Ebralidze, II, J.G. Egan, J. Poisson, N.O. Laschuk, F. Gaspari, E.B. Easton, O.V. Zenkina, ACS Appl Mater Interfaces, 9 (2017) 40438-40445. [2] N.O. Laschuk, Ebralidze, II, J. Poisson, J.G. Egan, S. Quaranta, J.T.S. Allan, H. Cusden, F. Gaspari, F.Y. Naumkin, E.B. Easton, O.V. Zenkina, ACS Appl Mater Interfaces, 10 (2018) 35334-35343. [3] J. Poisson, H.L. Geoffrey, I.I. Ebralidze, N.O. Laschuk, J.T.S. Allan, A. Deckert, E.B. Easton, O.V. Zenkina, The Journal of Physical Chemistry C, 122 (2018) 3419-3427. Figure 1

This paper investigates the effect of Zr, Hf, and Ta doping on the performances of Dye-sensitized solar cells (DSSCs) with photoanodes comprising mesoporous hierarchical anatase spheres. Morphology, structure, and optical properties of doped and undoped materials were examined by Field Emission Scanning Electron Microscopy, X-ray diffraction, and Diffuse Reflectance Spectroscopy, and materials’ characteristics were related to DSSC fundamental photovoltaic parameters by polarization curves (under illumination and dark conditions) and external quantum efficiency measurements. Photoanodes’ charge transport and recombination properties were investigated by Electrochemical Impedance Spectroscopy. Although doping were carried out by inserting a small amount (from 0.1 to 0.3 at %) of homo and aliovalent and electron-rich (with respect to Ti4+) cation, energy conversion efficiency turned out to be lower than pure anatase photoanodes. Electron-impurity scattering phenomena in conjunction with reduced specific surface area caused by the increased bulk free energy are believed to account for the efficiency drop. However, a small beneficial effect introduced by doping on the trap-mediated recombination mechanisms has been identified.

Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, a printed RF slot ring resonator is configured with a graphene thin-film for sensor application. The conductive losses in the graphene film are characterized by dielectric spectroscopy and considered in the design. The graphene sensing element comprising the slot ring can be integrated with control electronics as a passive wireless sensor node, but the sensor aspect is not addressed in this paper. The novelty of the paper is that RF losses are minimized by capacitively loading the ring at selective locations along its periphery. Dielectric spectroscopy is used to study variation in surface impedance of the film for various graphene loadings, and RF simulations are corroborated with measurements on graphene loaded slot ring resonators.

During the past 20 years, dye-sensitized solar cells (DSSCs) emerged and developed as a promising and low cost alternative to traditional photovoltaics. One of the main obstacles to mass-scale introduction of this technology is represented by their relatively modest conversion efficiency. In this paper, the authors propose and verify the possibility of improving the performance of the devices by taking advantage of the spontaneous formation of Schottky-type rectifying junctions between multi-walled carbon nanotubes and anatase nanoparticles in the preparation of DSSC photoanodes. These junctions improve the charge transport toward the anode with respect to the charge recombination phenomena. A model anatase-graphite Schottky diode was also prepared and characterized in order to verify on macroscopic scale the formation of a Schottky-type junction between the two materials. At 0.1 wt% of MWCNTs a 55% increase of efficiency with respect to DSSCs without MWCNTs has been obtained. The role of the optimum concentration of MWCNTs in the photoanode is discussed on the light of the DSSC electrical parameters taken up from various techniques.

Today’s world PV market is dominated by standard crystalline solar cells (so-called Al-BSF cells) and part of the market is shifting to PERC solar cells. The shift is obtained by introducing three additional process steps to the standard process (rear side cleaning, passivation and laser opening), and allows a gain of typically 1% absolute in efficiency. Next generation c-Si technologies should feature higher voltage solar cells with higher efficiency and less processing steps in the manufacturing, allowing for further cost reduction, both at the PV panel level and for the final cost of solar electricity. AMPERE, H2020 funded project, (http://www.ampere-h2020.eu/) focuses on technologies with such a potential and capitalizes on the high tech investments made in Europe over the last decade for establishing advanced manufacturing processes for crystalline silicon heterojunction (SHJ) solar cells and modules. A main cost factor in such cell processing, as expected, was found to be the silver based metallization. Estimating a silver paste consumption of 200mg, for a bifacial SHJ cell, and a silver paste cost conservatively estimated at 800 USD/kg for low-temperature paste, in a 23% efficiency cell, the silver cost will be around 3.0c$/Wp accounting for almost the 20% of the total industrial cost of the SHJ bifacial cell. Silver should be replaced on a large-scale basis by a more cost-effective material. Copper (Cu) is the intended substitute. The expected introduction of Cu into mass production is delayed mainly due to the big progress in screen printing and also due to some technical issues in reliability, adhesion that have to be resolved as also appropriate equipment and processes need to be available with the appropriate footprint and productivity. Comparing the state art of PV industrial plating a breakthrough plating process for SHJ copper metallization will be presented. Selective processing technique based on dynamic liquid drop/meniscus (DLD/DLM) allows metallization of solar cell fingers and bus bars without using any kind of lithography [1]. Figure 1.A presents the 2D view of how the DLD works. The system is composed, in a principle implementation, by an internal jetting outlet where a liquid flow is forced, and an external recalling inlet where by a depression the liquid is recalled back into the system. The input channel, confined by rigid wall (i.e. solid material), pumps a constant liquid flux that, depending on the input nozzle dimension, fixes the velocity of the liquid exiting the input channel. Due to a lower pressure in the surrounding of output channel, the airflow (gas) sustains the liquid (figure 1.A: black arrows in the red liquid) forming the DLD. The dynamic characteristics is due to the constantly refreshment of the liquid, during time, inside the drop. As the substrate gets in contact with the DLD, a DLM is formed, as shown in figure 1.B. Such technique allows to touch the surface of a solar cell only in specific defined positions and to perform electrochemical plating treatments in a localized manner. In DLM speed of liquid is in the meter per second range, like in a jet-plating technique, allowing to have fast deposition rate of metals. Due to the fast speed of liquid flow, the plating rate of copper is in the range of micron per seconds. In figure 1.C is shown an 100 micron width meniscus formed on glass substrate and the direction of movement of the DLM is indicated by the arrow. The ongoing result of EU Horizon2020 AMPERE project relative to copper metallization on ITO with fingers down to less than 60 micron width will be presented showing how by special reduction technique of ITO plus a thin barrier layer of nickel (figure 1.E and 1.D shows SEM cross-section of ITO reduced with thin layer of plated Ni), is possible without damaging the solar cell life time, obtain very good specific contact resistance (i.e. < 0.3mΩcm2) with 10 micron of copper and good adhesion (i.e. >2N/mm). Moreover, due to the fast plating condition, it will be shown that the equipment footprint can be interestingly reduced down to less than 18sqm for a 100MW line managing very low amounts of chemical. Due to its unique characteristics, DLD/DLM technique thanks to speed of processing, localized processing, small footprint and reduced chemical consumption, will represents a breakthrough in the market of plating for the solar cell applications. [1] M. Balucani, et al.; “New Selective Processing Technique for Solar Cells”, Energy Procedia (2013) 43, 54-65 Figure 1

The progression in the electronics industry is toward further minimization and the global semiconductor assembly community is striving for a robust replacement for leaded solders due to increased environmental regulations. A family of Pb-free solder alloys based on Sn-Ag-Cu (SAC) compositions has shown promise, but due to reliability issues in certain assembly and operating environments, quaternary (Mn, Ni, Zn, and Al-doped SAC) solders are currently under investigation. With more computing power, higher performance is needed for smaller areas. The ball-grid-array (BGA) packaging system with a decreased size, is likely to be replaced by chip-scale packages (CSPs) (i.e. µBGA) and Copper Pillar Bumps (CPBs). There are several methods to form solder bumps such as screen printing, evaporation and electroplating. As the pitch and the bump size decrease, electroplating becomes the only efficient way to fabricate bumps with small size, fine pitch and low cost. Electroplating is considered to be the only feasible technique to form the copper pillar and the solder cap to realize the CPBs. Currently, solder electroplating is limited mainly to binary compound plating and there exist no stable solutions for electroplating of ternary alloys due to a large gap in electrochemical reduction potentials between different elements. For example, in order to perform SAC electroplating Karim et al. had to use sequential plating from two separate binary SnCu and SnAg plating solutions [1]. However, if developed, ternary alloy plating solutions may not be practical under manufacturing conditions considering that it is hard to maintain bath and alloy composition even for binary plating solutions. Obviously the development of a plating solution for quaternary alloy is even less probable. In order to deposit alloy with precise composition, multilayer electroplating method is proposed instead. The method lies in the sequential electroplating of each of the solder components from a separate bath and a consequent reflow to form uniform alloy. Unfortunately to warrantee the reliability the electroplating sequence should be carefully watched [2]. To overcome inter-diffusion limitation and achieve a uniform and fast reflow, low thickness of each layer is necessary and a proportional increase of layers number makes the process time-consuming and impractical from a conventional electroplating point of view due to multiple switching between solution baths. The present work will show how using a new concept in electroplating, based on multiple Dynamic Liquid Drop/Meniscus (DLD/DLM), is possible to realize multilayer approach to plate binary, ternary and even quaternary solder alloy at high throughput, high precision and low cost. The DLD/DLM [3] represents a constantly refreshed confined electrolyte volume in touch with a substrate surface. The plating concept lies in assembling multiple independent DLD/DLM in a sequential array (one or many for each plating component intercalated by a rinse DLD/DLM) into a multiple plating head. Thus scanning the plating head over the wafer surface will allow consequent plating of a layer of each of the component. Each pass of the plating head leads to deposition of the multilayered structure representing consequent components layers (grains) with a required proportion. Total thickness of the alloy depends on the number of passages and can be varied in a wide range. Using the proposed technique various solder compositions were deposited. As a proof-of-concept, SAC305 and SAC405 layers with 30µm thickness were deposited containing more than 350 layers of each element. A detailed investigation of SAC and quaternary SAC+Mn alloys composition will be presented; EDX analysis before and after reflow proving that the high number of layers an homogenous solder is obtained independently of metal deposition sequence and even without reflow. The proposed breakthrough technique offers the unique opportunity to deposit any kind of binary, ternary and quaternary Pb-free alloy solder from single bath solutions without any kind of cross contamination. Such technique poses a key milestone to obtain ternary and/or quaternary Pb-free solder alloy for the CSPs and CPBs allowing to tune the correct solder alloy in order to finally solve reliability issues. [1] Z. S. Karim and J. Martin, “Lead-free solder bump technologies for flip-chip packaging applications”, SMTA (2001). [2] Qinghua Zhao, Anmin Hu, Ming Li, Jiangyan Sun, “Effect of electroplating layer structure on shear property and microstructure of multilayer electroplated Sn-3.5Ag solder bumps” Microelectronics Reliability 53 (2013) 321–326 [3] Konstantin Kholostov, et al. “High uniformity and high speed copper pillar plating technique” IEEE 64th Electronic Components and Technology Conference (ECTC), 2014, 1571-1576 Figure 1 shows the SEM pictures and EDX analysis of SAC 305 μBGA by multiple DLD/DLM technique. Figure 1

Graphene is a monolayer of carbon atoms which exhibits remarkable electronic and mechanical properties. Graphene based nano-materials have gained a lot of interest for many applications. In this paper, inks with three different graphene concentrations (12.5, 25, and 33 wt % in graphene) were prepared and deposited by screen printing. A detailed investigation of films’ surface morphology using Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) revealed that the graphene films present a homogeneous dispersion of the filler with a comparatively lower surface roughness at higher concentrations and negligible agglomerates. The films were then printed between copper electrodes on FR-4 substrate (trade name for glass-reinforced epoxy laminate material), commonly used in Radio Frequency (RF) circuits, and the measured scattering parameters analyzed. Finally, the reflection coefficient of a patch antenna, fabricated on FR-4 substrate with and without a stub loaded by a thin film were measured. The difference of the resonant frequency due to the different interaction between graphene flakes and polymer binders shows attractive features of functionalized graphene films for chemical and bio-sensing applications.

Low-cost carbons derived from recycled materials have been gaining attention recently for their potentials as filler in composites and in other applications. Biochar is one such carbon produced from the pyrolysis of biomasses or other biogenic wastes. In this work, biochar and activaed biochar were used as filler (20 wt%) to produce Epoxy resin-based composites. The activated biochar (12.5 wt%) was also used to produce screen printed thin films. Electrical characteristics of both composites and thin films were investigated.

In this paper, the tunability of a patch antenna using Multi-Walled Carbon Nanotube (MWCNT) thin film deposition is addressed. Screen printing technique is used to insert a CNT film in a loading stub connected to the antenna patch. The variation of the CNT surface impedance modifies the resonant frequency by about 230 MHz from the reference value, as revealed by comparison of return loss measured with and without the CNT loading. Radiation pattern for these two cases is also studied for various layer thicknesses of the film.

The present work aims at optimizing titanium dioxide morphology for dye-sensitized solar cells applications. Five different anatase phase mesoporous titanias were prepared and tested as photoanodes in dye-sensitized solar cells. The materials were prepared by using a template approach. Two materials were synthesized by using monodisperse silica nanospheres and the other three using two different organic templating agents (Pluronic P123 and Brij 58). A complete characterization of the obtained materials was performed by powder XRD, FEG-SEM, UV-Vis reflectance spectroscopy, BET surface area measurements, and TG-DTA. Several cells were assembled using N719 as dye and a nonvolatile electrolyte based on benzonitrile. The cells were tested by means ofJ-Vcurves under simulated solar radiation, IPCE, and dark current measurements. The highest efficiencies were achieved with titania prepared by using Pluronic P123 as template (ηmax=6.8%), while the lowest efficiencies were recorded with using titania samples prepared with the silica nanospheres template (ηmin=5.7%). The different performances of the samples are examined and discussed.

Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1–0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J–V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms.