- Portugal
Artur Ferreira
University of Aveiro, ESTGA, Faculty Member
... Novel Silicate Anion: Si 8 O 22 12 - . Hydrothermal Synthesis and X-ray Powder Structure of Three New Niobium Silicates. Miguel A. Salvadó, Pilar Pertierra, and Santiago García-Granda, Sergei A. Khainakov and José R. García, Anatoly... more
... Novel Silicate Anion: Si 8 O 22 12 - . Hydrothermal Synthesis and X-ray Powder Structure of Three New Niobium Silicates. Miguel A. Salvadó, Pilar Pertierra, and Santiago García-Granda, Sergei A. Khainakov and José R. García, Anatoly I. Bortun and Abraham Clearfield. ...
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ABSTRACT The synthesis of a new potassium titanosilicate, K4Ti2Si6O18 (Ti–AV-11), possessing the crystal structure of potassium stannosilicate AV-11, has been reported. The unit cell of this material is trigonal, space group R3 (no. 146),... more
ABSTRACT The synthesis of a new potassium titanosilicate, K4Ti2Si6O18 (Ti–AV-11), possessing the crystal structure of potassium stannosilicate AV-11, has been reported. The unit cell of this material is trigonal, space group R3 (no. 146), Z=3, a=10.012, c=14.8413Å, γ=120°, V=1289Å3. The structure of AV-11 is built up of MO6 (M=Sn, Ti) octahedra and SiO4 tetrahedra by sharing corners. The SiO4 tetrahedra form helix chains, periodically repeating every six tetrahedra. These chains extend along the [001] direction and are linked by isolated MO6 octahedra, thus producing a mixed octahedral–tetrahedral oxide framework. AV-11 materials have been further characterized by bulk chemical analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), 29Si and 119Sn magic-angle spinning (MAS) NMR spectroscopy.
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Research Interests: Engineering, Materials Science, Photochemistry, Lanthanide, Magnetic Resonance Spectroscopy, and 12 moreMedicine, Photoluminescence, Physical sciences, Luminescence, The, Thermogravimetry, CHEMICAL SCIENCES, Ion, Scanning Electron Microscope, Molecular weight, Sensitivity and Specificity, and Silicates
ABSTRACT A zirconosilicate (Na0.2K1.8ZrSi3O9·H2O) analogue of the small-pore mineral kostylevite (AV-8) has been prepared via hydrothermal synthesis. The thermal transformation of microporous zirconosilicates synthetic petarasite [AV-3,... more
ABSTRACT A zirconosilicate (Na0.2K1.8ZrSi3O9·H2O) analogue of the small-pore mineral kostylevite (AV-8) has been prepared via hydrothermal synthesis. The thermal transformation of microporous zirconosilicates synthetic petarasite [AV-3, Na5Zr2Si6O18(Cl,OH)·2H2O] and synthetic umbite (AM-2, K2ZrSi3O9·H2O) has been studied by powder XRD, TGA, 29Si, and single- and triple-quantum 23Na MAS NMR. The structure of AV-8 and the structures of synthetic analogues of the dense minerals parakeldyshite (Na2ZrSi2O7) and wadeite (K2ZrSi3O9) obtained via calcination of AV-3 and AM-2, respectively, have been Rietveld refined and fully characterized by 29Si and 23Na solid-state NMR.
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ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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Two new large‐pore sodium vanadium silicates, denoted AM‐15 and AM‐17 (Aveiro‐Manchester, structures number 15 and 17) with framework composition Na6Si14V4O39 and Na4CaSi10V2O27, respectively, are reported. Electron paramagnetic resonance... more
Two new large‐pore sodium vanadium silicates, denoted AM‐15 and AM‐17 (Aveiro‐Manchester, structures number 15 and 17) with framework composition Na6Si14V4O39 and Na4CaSi10V2O27, respectively, are reported. Electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR) and diffuse reflectance ultraviolet‐visible (DR UV/Vis) spectroscopy reveal that as‐prepared AM‐15 contains both VIV and VV in a square pyramidal and tetrahedral coordination, respectively, while AM‐17 contains predominantly octahedral VIV. The thermal stability of AM‐15 in air is modest (ca. 380 °C), while AM‐17 is stable up to 450 °C. The acid‐base and redox properties of AM‐17 have been assessed by the conversion of isopropanol and ethanol oxidation, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
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Publisher Summary This chapter discusses the synthesis and characterization of novel microporous framework cerium and europium silicates. Both materials display interesting photoluminescence properties and present potential for... more
Publisher Summary This chapter discusses the synthesis and characterization of novel microporous framework cerium and europium silicates. Both materials display interesting photoluminescence properties and present potential for applications in optoelectronics. This chapter also illustrates the possibility of combining in a given framework silicate microporosity and optical activity.
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The hydrothermal synthesis and structural characterization of layered lanthanide silicates, K(3)[M(1-a)Ln(a)Si(3)O(8)(OH)(2)] (M = Y(3+), Tb(3+); Ln = Eu(3+), Er(3+), Tb(3+), and Gd(3+)), named AV-22 materials, are reported. The structure... more
The hydrothermal synthesis and structural characterization of layered lanthanide silicates, K(3)[M(1-a)Ln(a)Si(3)O(8)(OH)(2)] (M = Y(3+), Tb(3+); Ln = Eu(3+), Er(3+), Tb(3+), and Gd(3+)), named AV-22 materials, are reported. The structure of these solids was elucidated by single-crystal (180 K) and powder X-ray diffraction and further characterized by chemical analysis, thermogravimetry, scanning electron microscopy, (29)Si MAS NMR, and photoluminescence spectroscopy. The Er-AV-22 material is a room-temperature infrared phosphor, while Tb- and Eu-AV-22 are visible emitters with output efficiencies comparable to standards used in commercial lamps. The structure of these materials allows the inclusion of a second (or even a third) type of Ln(3+) ion in the framework and, therefore, the fine-tuning of their photoluminescent properties. For the mixed Tb(3+)/Eu(3+) materials, evidence has been found of the inclusion of Eu(3+) ions in the interlayer space by replacing K+ ions, further allowing the activation of Tb(3+)-to-Eu(3+) energy transfer mechanisms. The occurrence probability of such mechanisms ranges from 0.62 (a = 0.05) to 1.20 ms(-1) (a = 0.1) with a high energy transfer efficiency (0.73 and 0.84, respectively).
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Bacterial cellulose (BC) has recently been the subject of a considerable amount of research, not only for its environmentally friendly biosynthesis, but also for its high potential in areas such as biomedicine or biomaterials. A symbiotic... more
Bacterial cellulose (BC) has recently been the subject of a considerable amount of research, not only for its environmentally friendly biosynthesis, but also for its high potential in areas such as biomedicine or biomaterials. A symbiotic relationship between a photosynthetic microalga, Chlamydomonas debaryana, and a cellulose producer bacterium, Komagataeibacter saccharivorans, was established in order to obtain a viable and active biofilm. The effect of the growth media composition ratio on the produced living material was investigated, as well as the microalgae biomass quantity, temperature, and incubation time. The optimal temperature for higher symbiotic biofilm production was 30 °C with an incubation period of 14 days. The high microalgae presence, 0.75% w/v, and 60:40 HS:BG-11 medium (v/v) induced a biofilm microalgae incorporation rate of 85%. The obtained results report, for the first time, a successful symbiotic interaction developed in situ between an alkaline photosynthe...
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Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and... more
Polymeric foams can be found virtually everywhere due to their advantageous properties compared with counterparts materials. Possibly the most important class of polymeric foams are polyurethane foams (PUFs), as their low density and thermal conductivity combined with their interesting mechanical properties make them excellent thermal and sound insulators, as well as structural and comfort materials. Despite the broad range of applications, the production of PUFs is still highly petroleum-dependent, so this industry must adapt to ever more strict regulations and rigorous consumers. In that sense, the well-established raw materials and process technologies can face a turning point in the near future, due to the need of using renewable raw materials and new process technologies, such as three-dimensional (3D) printing. In this work, the fundamental aspects of the production of PUFs are reviewed, the new challenges that the PUFs industry are expected to confront regarding process metho...
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The aim of this study was to enhance the thermal comfort properties of crude glycerol (CG) derived polyurethane foams (PUFs) using phase change materials (PCMs) (2.5⁻10.0% ()) to contribute to the reduction of the use of non-renewable... more
The aim of this study was to enhance the thermal comfort properties of crude glycerol (CG) derived polyurethane foams (PUFs) using phase change materials (PCMs) (2.5⁻10.0% ()) to contribute to the reduction of the use of non-renewable resources and increase energy savings. The main challenge when adding PCM to PUFs is to combine the low conductivity of PUFs whilst taking advantage of the heat released/absorbed by PCMs to achieve efficient thermal regulation. The solution considered to overcome this limitation was to use expandable graphite (EG) (0.50⁻1.50% ()). The results obtained show that the use of PCMs increased the heterogeneity of the foams cellular structure and that the incorporation of PCMs and EG increased the stiffness of the ensuing composite PUFs acting as filler-reinforcing materials. However, these fillers also caused a substantial increase of the thermal conductivity and density of the ensuing foams which limited their thermal energy storage. Therefore, numerical si...
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Bacterial cellulose/polyaniline (BC/PANi) blends present a great potential for several applications. The current study evaluates the impact of using different BC matrixes (drained, freeze-dried and regenerated) and different synthesis... more
Bacterial cellulose/polyaniline (BC/PANi) blends present a great potential for several applications. The current study evaluates the impact of using different BC matrixes (drained, freeze-dried and regenerated) and different synthesis conditions (in situ and ex situ) to improve the inherent properties of BC, which were monitored through FTIR-ATR, EDX, XRD, SEM, AFM, swelling, contact angle measurement and IGC. The employment of in situ polymerization onto drained BC presented the most conductive membrane (1.4 × 10 S/cm). The crystallinity, swelling capacity, surface energy and acid/base behavior of the BC membranes is substantially modified upon PANi incorporation, being dependent on the BC matrix used, being the freeze-dried BC blends the ones with highest crystallinity (up to 54%), swelling capacity (up to 414%) and surface energy (up to 75.0 mJ/m). Hence, this work evidenced that the final properties of the BC/PANi blends are greatly influenced by both the BC matrixes and synthes...
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INORGANIC microporous framework solids such as zeolites are of considerable technological importance as shape-selective catalysts, ion-exchange materials and molecular sieves1. Most microporous materials known until recently were... more
INORGANIC microporous framework solids such as zeolites are of considerable technological importance as shape-selective catalysts, ion-exchange materials and molecular sieves1. Most microporous materials known until recently were silicates, aluminosilicates1 or ...
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ABSTRACT Ecopolyol production from acid liquefaction of cork powder was studied for the first time using PEG 400 and glycerol as liquefaction solvents in the presence of sulfuric acid at moderate temperature and atmospheric pressure. The... more
ABSTRACT Ecopolyol production from acid liquefaction of cork powder was studied for the first time using PEG 400 and glycerol as liquefaction solvents in the presence of sulfuric acid at moderate temperature and atmospheric pressure. The effect of the temperature, concentration of catalyst, and time on the liquefaction yield has been investigated using a fixed set of reaction conditions namely, a liquefaction solvent mixture/cork powder ratio of 5/1 and a solvent mixture PEG 400/glycerol ratio of 90/10. The full-factorial design of experiments (DOE) 23 was applied to obtain an optimized set of liquefaction conditions aiming at minimizing the residue content. The minimum residue contents experimentally obtained in this study were 29 wt %, related to cork powder, which were achieved at 150 °C, 4 wt % of sulfuric acid, and 60 min. This value corresponds to 5 wt % of residue per total mass of reaction product. The polyols obtained under optimal conditions present similar characteristics (hydroxyl number value 219 mgKOH/gpolyol and viscosity 2875 cP, at 25 °C) to those of petroleum-based polyols typically used in the polyurethane foam industry.
ABSTRACT BACKGROUND: Based on the biorefinery concept, themain focus of this work was the increase in value of spent coffee grounds via an acid liquefaction process using polyhydric solvents in the presence of sulfuric acid, at moderate... more
ABSTRACT BACKGROUND: Based on the biorefinery concept, themain focus of this work was the increase in value of spent coffee grounds via an acid liquefaction process using polyhydric solvents in the presence of sulfuric acid, at moderate temperature. For that purpose the effect of temperature, sulfuric acid concentration and time on biomass conversion was studied using design of experiments combined with statistical analysis. RESULTS: The ANOVA results (95% confidence level) showed that temperature is the factor with most influence on biomass conversion, within the studied range, while reaction times above 40 min don’t seem to bring significant advantages. The maximum conversion obtained in this studywas 70wt% whichwas achieved at 160∘C, 4wt%of catalyst and 80min. The polyol obtained using these conditions presented a hydroxyl number value of 199 mg KOH / g polyol and a viscosity of 390 cP, at 25∘C. CONCLUSION: This work showed that it is possible to convert spent coffee grounds into liquid polyols via an acid liquefaction process atmoderate temperature and autogeneous pressure. These polyols have similar properties to those of petroleum-based polyols typically used in the polyurethane foam industry.
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ABSTRACT The aim of this study was to evaluate the possibility of using polyols derived from liquefied cork in the production of novel bio-based polyurethane foams (PUFs). For that propose, different liquefaction conditions were carry out... more
ABSTRACT The aim of this study was to evaluate the possibility of using polyols derived from liquefied cork in the production of novel bio-based polyurethane foams (PUFs). For that propose, different liquefaction conditions were carry out at atmospheric pressure and moderate temperature where PEG and glycerol were used as solvents and sulfuric acid used as catalyst. The ensuing polyols were used to produce foams which were characterized by structural, morphological, thermal and mechanical analyses to demonstrate that liquefaction conditions play a crucial role on the properties of the ensuing foams. The resulting foams exhibited the typical cellular structure of PUFs with low densities (57.4 – 70.7 kg/m3) and low thermal conductivity (0.038-0.040 W/mk). However, the mechanical properties differed significantly depending on the liquefaction conditions. The best stress–strain results were obtained for the PUFs prepared using the polyol with lowest IOH and water content (Young modulus 475.0 kPa, compressive stress (σ10%) 34.6 kPa and toughness 7397.1 J/m3). This PUF was thermally stable up to 200 ºC and presented a glass transition temperature around 27 ºC. The results obtained demonstrated that these polyols from liquefied cork yield PUFs that are adequate materials for insulation applications.
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Ecopolyols production from acid liquefaction of cork powder and coffee grounds was investigated using PEG#400 and glycerol in the presence of sulfuric acid. The liquefaction conditions were optimized by statistical analysis using a 23... more
Ecopolyols production from acid liquefaction of cork powder and coffee grounds was investigated using PEG#400 and glycerol in the presence of sulfuric acid. The liquefaction conditions were optimized by statistical analysis using a 23 full-factorial design with temperature, sulfuric acid concentration and time as process parameters. The minimum residue contents for cork powder (30%) and coffee grounds (28%) were achieved at 150 ºC, 4% of sulfuric acid and 60 min and 160 ºC, 4% of sulfuric acid and 80 min, respectively. The obtained ecopolyols presented similar characteristics to those of petroleum-based polyols typically used in semi-rigid polyurethane foam formulations.
INORGANIC microporous framework solids such as zeolites are of considerable technological importance as shape-selective catalysts, ion-exchange materials and molecular sieves1. Most microporous materials known until recently were... more
INORGANIC microporous framework solids such as zeolites are of considerable technological importance as shape-selective catalysts, ion-exchange materials and molecular sieves1. Most microporous materials known until recently were silicates, aluminosilicates1 or ...
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Abstract. The production of polymers, both the synthesis and the solvent removal during processing demands the knowledge of the phase equilibria establishing for process optimization. This communication presents two experimental works for... more
Abstract. The production of polymers, both the synthesis and the solvent removal during processing demands the knowledge of the phase equilibria establishing for process optimization. This communication presents two experimental works for teaching Physical Chemistry of polymer systems at ...
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Research Interests: Engineering, Materials Engineering, Chemical Engineering, Condensed Matter Physics, Analytical Chemistry, and 11 moreInorganic Chemistry, Organic Chemistry, Technology, Coordination Chemistry, Organometallic Chemistry, Physical sciences, The, CHEMICAL SCIENCES, Transition metal chemistry, Thin Solid Films, and Inorganic Biochemistry
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Lignocellulosic biomass residues represent a renewable, biodegradable, abundant and cheap source of raw materials for the chemical industry without affecting food and feed supplies [1]. The polyurethane industries are aware of this trend... more
Lignocellulosic biomass residues represent a renewable, biodegradable, abundant and cheap source of raw materials for the chemical industry without affecting food and feed supplies [1]. The polyurethane industries are aware of this trend and have been exploring the development of low-cost polyols from different biomass resources by liquefaction methodologies. Recently, there have been increasing publications about the valorization of lignocellulosic residues (wood [4], corn [5], wheat straw [6], cotton [7], lignin [8] and rapeseed [9]) by acid liquefaction processes, using polyhydric alcohols as solvent to obtain liquid ecopolyols rich in hydroxyl groups that can be used as starting materials in the production of several polymeric products (for example, polyurethane foams). Cork, the bark of oak (Quercus suber L.), is mainly composed of suberin (30-60%), lignin (19-22%), polysaccharides (12-20%) and extractives (9-20%), including aliphatic, phenolic and triterpenenic compounds [10]....