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Keywords = nanometric pores

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15 pages, 4162 KiB  
Article
Alginate/k-Carrageenan Interpenetrated Biopolymeric Aerogels for Nutraceutical Drug Delivery
by Alessandra Zanotti, Lucia Baldino, Ernesto Reverchon and Stefano Cardea
Gels 2025, 11(6), 393; https://doi.org/10.3390/gels11060393 - 27 May 2025
Viewed by 474
Abstract
Bioactive compounds of natural origin are central to the development of nutraceutical formulations. To improve their stability and to target their delivery to the intestinal or colonic tract, alginate/k-carrageenan spherical gels have been produced at different volumetric ratios (100/0, 70/30, 50/50, 30/70, and [...] Read more.
Bioactive compounds of natural origin are central to the development of nutraceutical formulations. To improve their stability and to target their delivery to the intestinal or colonic tract, alginate/k-carrageenan spherical gels have been produced at different volumetric ratios (100/0, 70/30, 50/50, 30/70, and 0/100 v/v), by means of solution dripping and external gelation. Different drying methods were compared, and only through supercritical technologies was it possible to achieve interpenetrated networks that feature nanometric pore size distribution. Hybrid aerogels inherited the most relevant characteristics of alginate and k-carrageenan: they showed remarkable water uptake capacity (e.g., 50.60 g/g), and stability in aqueous media over large timespans. Naringin release tests in simulated intestinal and colonic fluids proved that it is possible to target drug delivery by choosing intermediate alginate/k-carrageenan ratios. Overall, by means of supercritical gel drying, it is possible to generate advanced biopolymeric aerogels, yielding fully natural interpenetrated networks that valorize the most compelling properties of each species involved. Full article
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20 pages, 4493 KiB  
Article
Copper Molybdate-Catalyzed Esterification of Levulinic Acid: A Heterogeneous Approach for Biofuel Synthesis
by Alyne Pereira de Oliveira Ribeiro, Wyvirlany Valente Lobo, Talles André Feitosa de Carvalho, José Milton Elias de Matos, Flávio Augusto de Freitas, Yurimiler Leyet Ruiz, Robert S. Matos, Ştefan Ţălu, Henrique Duarte da Fonseca Filho, Lianet Aguilera Domínguez, Walter Ricardo Brito and Francisco Xavier Nobre
Catalysts 2025, 15(4), 357; https://doi.org/10.3390/catal15040357 - 6 Apr 2025
Cited by 1 | Viewed by 742
Abstract
The catalytic esterification of levulinic acid (LA) to methyl levulinate (ML) was investigated using copper molybdate (Cu3(MoO4)2(OH)2) as a heterogeneous catalyst. The catalyst, synthesized via chemical precipitation, exhibited a monoclinic structure with self-assembled nanoplates forming [...] Read more.
The catalytic esterification of levulinic acid (LA) to methyl levulinate (ML) was investigated using copper molybdate (Cu3(MoO4)2(OH)2) as a heterogeneous catalyst. The catalyst, synthesized via chemical precipitation, exhibited a monoclinic structure with self-assembled nanoplates forming spherical mesostructures. Structural characterization confirmed its high crystallinity, while textural analysis revealed a BET surface area of 70.55 m2 g−1 with pore sizes in the nanometric range (1–6 nm). The catalytic performance was systematically evaluated under varying reaction conditions, including temperature, catalyst dosage, reaction time, methanol-to-LA molar ratio, alcohol type, and catalyst reusability. Optimal conversion of 99.3% was achieved at 100 °C, a 1:20 methanol-to-LA molar ratio, 5% catalyst loading, and a reaction time of 4 h. Comparative analysis with other heterogeneous catalysts demonstrated superior efficiency and stability of Cu3(MoO4)2(OH)2, with minimal activity loss over four reuse cycles (final conversion of 77.1%). Mechanistic insights suggest that its high activity is attributed to Lewis and Brønsted acid sites, facilitating efficient esterification. This study underscores the potential of copper molybdate as a sustainable and recyclable catalyst for biofuel additive synthesis, advancing green chemistry strategies for biomass valorization. Full article
(This article belongs to the Special Issue Sustainable Catalysis for Green Chemistry and Energy Transition)
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12 pages, 21558 KiB  
Article
Ceramic Nanofiltration Membranes: Creating Nanopores by Calcination of Atmospheric-Pressure Molecular Layer Deposition Grown Titanicone Layers
by Harpreet Sondhi, Mingliang Chen, Michiel Pieter Nijboer, Arian Nijmeijer, Fred Roozeboom, Mikhael Bechelany, Alexey Kovalgin and Mieke Luiten-Olieman
Membranes 2025, 15(3), 86; https://doi.org/10.3390/membranes15030086 - 8 Mar 2025
Viewed by 1728
Abstract
Ceramic membrane technology, whether applied as a stand-alone separation technology or in combination with energy-intensive approaches like distillation, is a promising solution for lower energy alternatives with minimal carbon footprints. To improve the separation of solutes in the nanofiltration range from industrial wastewater [...] Read more.
Ceramic membrane technology, whether applied as a stand-alone separation technology or in combination with energy-intensive approaches like distillation, is a promising solution for lower energy alternatives with minimal carbon footprints. To improve the separation of solutes in the nanofiltration range from industrial wastewater streams, ceramic nanofiltration (NF) membranes with reproducible sub-nanometre pore sizes are required. To achieve this, the emerging technique of molecular layer deposition (MLD) is employed to develop ceramic NF membranes, and its efficiency and versatility make it a powerful tool for preparing uniform nanoscale high-porosity membranes. Our work, which involved vapor-phase titanium tetrachloride as a precursor and ethylene glycol as a co-reactant, followed by calcination in air at 350 °C, resulted in NF membranes with pore sizes (radii) around ~0.8 ± 0.1 nm and a demineralized water permeability of 13 ± 1 L·m−2·h−1·bar−1.The high-water flux with >90% rejection of polyethylene glycol molecules with a molecular size larger than 380 ± 6 Dalton indicates the efficiency of the MLD technique in membrane functionalization and size-selective separation processes, and its potential for industrial applications. Full article
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15 pages, 3243 KiB  
Article
Optimization of Laser Based-Powder Bed Fusion Parameters for Controlled Porosity in Titanium Alloy Components
by Emanuele Vaglio, Federico Scalzo, Marco Sortino, Giovanni Totis, Roberto Cremonese, Massimiliano Boccia and Maila Danielis
Materials 2024, 17(22), 5572; https://doi.org/10.3390/ma17225572 - 14 Nov 2024
Viewed by 1313
Abstract
Laser based-powder bed fusion (LB-PBF) enables fast, efficient, and cost-effective production of high-performing products. While advanced functionalities are often derived from geometric complexity, the capability to tailor material properties also offers significant opportunities for technical innovation across many fields. This study explores the [...] Read more.
Laser based-powder bed fusion (LB-PBF) enables fast, efficient, and cost-effective production of high-performing products. While advanced functionalities are often derived from geometric complexity, the capability to tailor material properties also offers significant opportunities for technical innovation across many fields. This study explores the optimization of the LB-PBF process parameters for producing Ti6Al4V titanium alloy parts with controlled porosity. To this end, cuboid and lamellar samples were fabricated by systematically varying laser power, hatch distance, and layer thickness according to a full factorial Design of Experiments, and the resulting specimens were thoroughly characterized by analyzing envelope porosity, surface roughness and waviness, surface morphology, and surface area. A selection of specimens was further examined using small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) to investigate the atomic structure and nanometric porosity of the material. The results demonstrated the possibility to finely control the porosity and surface characteristics of Ti6Al4V within specific LB-PBF process ranges. The pores were found to be mostly closed even for thin walls, while the surface roughness was recognized as the primary factor impacting the surface area. The lamellar samples obtained by exposing single scan tracks showed nearly an order-of-magnitude increase in both surface area and pore volume, thereby laying the groundwork for the production of parts with optimized porosity. Full article
(This article belongs to the Special Issue The Additive Manufacturing of Metallic Alloys)
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14 pages, 4266 KiB  
Article
Crosslinked Polydiallyldimethylammonium Chloride Adsorbent for the Selective Separation of Rhenium Ions from Pregnant Leach Solutions
by Mohammadbagher Fathi, Mehdi Mahmoudian, Richard Diaz Alorro and Mostafa Chegini
Materials 2024, 17(11), 2737; https://doi.org/10.3390/ma17112737 - 4 Jun 2024
Viewed by 1388
Abstract
The depletion of valuable mineral reserves has rendered effluents generated from mining and industrial processing activities a promising resource for the production of precious elements. The synthesis and improvement of new adsorbents to extract valuable compounds from industrial wastes and pregnant leach solutions, [...] Read more.
The depletion of valuable mineral reserves has rendered effluents generated from mining and industrial processing activities a promising resource for the production of precious elements. The synthesis and improvement of new adsorbents to extract valuable compounds from industrial wastes and pregnant leach solutions, besides increasing wealth, can play a significant role in reducing environmental concerns. In this work, a new and low-cost adsorbent for the selective extraction of rhenium (perrhenate ions, ReO4) was synthesized by the free-radical polymerization (FRP) of a diallyl dimethylammonium chloride monomer (quaternary amine) in the presence of a crosslinker. Various methods were employed to characterize the polymeric adsorbent. The results revealed that the designed polymeric adsorbent had a high surface area and pores with nano-metric dimensions and a pore volume of 6.4 × 10−3 cm3/g. Four environments—single, binary, multicomponent, and real solutions—were applied to evaluate the adsorbent’s performance in the selective separation of Re. Additionally, these environments were used to understand the behavior of molybdenum ions, the primary competitors of perrhenate ions in the ion exchange process. In competitive conditions, using variations in qe,mix/qe, an antagonism phenomenon (qe,mix/qe < 1) occurred due to the inhibitory effect of surface-adsorbed molybdenum ions on the binding of the perrhenate ions. However, across all conditions, the separation values for Re were higher than those for the other studied elements (Mo, Cu, Fe). Full article
(This article belongs to the Special Issue Adsorption Materials and Their Applications)
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11 pages, 5816 KiB  
Article
Photoluminescent Nanocellulosic Film for Selective Hg2+ Ion Detection
by Jing Sun, Wenwen Fang, Afroza Akter Liza, Rui Gao, Junlong Song, Jiaqi Guo and Orlando J. Rojas
Polymers 2024, 16(11), 1583; https://doi.org/10.3390/polym16111583 - 3 Jun 2024
Cited by 1 | Viewed by 1189
Abstract
We developed a highly sensitive solid-state sensor for mercury detection by stabilizing red-sub-nanometric fluorescent gold nanoclusters (AuNC, 0.9 ± 0.1 nm diameter) with bovine serum albumin in a matrix composed of cellulose nanofibrils (CNF) (BSA-AuNC/CNF). The main morphological and optical features of the [...] Read more.
We developed a highly sensitive solid-state sensor for mercury detection by stabilizing red-sub-nanometric fluorescent gold nanoclusters (AuNC, 0.9 ± 0.1 nm diameter) with bovine serum albumin in a matrix composed of cellulose nanofibrils (CNF) (BSA-AuNC/CNF). The main morphological and optical features of the system were investigated via atomic force/transmission electron microscopy and UV-Vis/fluorescence spectroscopy. The hybrid film (off-white and highly transparent) showed strong photoluminescene under UV irradiation. The latter is assigned to the AuNC, which also increase the ductility of the emitting film, which was demonstrated for high sensitivity Hg2+ detection. When used as a sensor system, following AuNC printing on CNF hybrid films, a limit of detection <10 nM was confirmed. What is more, nanocellulose films have a high pore structure and selective separation properties, showcasing a wide range of potential applications in many fields such as water treatment and oil–water separation. Full article
(This article belongs to the Section Circular and Green Sustainable Polymer Science)
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27 pages, 1430 KiB  
Review
Sol–Gel Technologies to Obtain Advanced Bioceramics for Dental Therapeutics
by Xiaozhe Song, Juan J. Segura-Egea and Aránzazu Díaz-Cuenca
Molecules 2023, 28(19), 6967; https://doi.org/10.3390/molecules28196967 - 7 Oct 2023
Cited by 14 | Viewed by 5026
Abstract
The aim of this work is to review the application of bioceramic materials in the context of current regenerative dentistry therapies, focusing on the latest advances in the synthesis of advanced materials using the sol–gel methodology. Chemical synthesis, processing and therapeutic possibilities are [...] Read more.
The aim of this work is to review the application of bioceramic materials in the context of current regenerative dentistry therapies, focusing on the latest advances in the synthesis of advanced materials using the sol–gel methodology. Chemical synthesis, processing and therapeutic possibilities are discussed in a structured way, according to the three main types of ceramic materials used in regenerative dentistry: bioactive glasses and glass ceramics, calcium phosphates and calcium silicates. The morphology and chemical composition of these bioceramics play a crucial role in their biological properties and effectiveness in dental therapeutics. The goal is to understand their chemical, surface, mechanical and biological properties better and develop strategies to control their pore structure, shape, size and compositions. Over the past decades, bioceramic materials have provided excellent results in a wide variety of clinical applications related to hard tissue repair and regeneration. Characteristics, such as their similarity to the chemical composition of the mineral phase of bones and teeth, as well as the possibilities offered by the advances in nanotechnology, are driving the development of new biomimetic materials that are required in regenerative dentistry. The sol–gel technique is a method for producing synthetic bioceramics with high purity and homogeneity at the molecular scale and to control the surfaces, interfaces and porosity at the nanometric scale. The intrinsic nanoporosity of materials produced by the sol–gel technique correlates with the high specific surface area, reactivity and bioactivity of advanced bioceramics. Full article
(This article belongs to the Collection Porous Materials)
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18 pages, 3122 KiB  
Article
New Triple Metallic Carbonated Hydroxyapatite for Stone Surface Preservation
by Lorena Iancu, Ramona Marina Grigorescu, Rodica-Mariana Ion, Madalina Elena David, Luminita Predoana, Anca Irina Gheboianu and Elvira Alexandrescu
Coatings 2023, 13(8), 1469; https://doi.org/10.3390/coatings13081469 - 21 Aug 2023
Cited by 3 | Viewed by 1801
Abstract
This paper presents the synthesis of the triple substituted carbonated hydroxyapatite with magnesium, strontium and zinc (Mg-Sr-Zn-CHAp), as well as its structural, morphological and compositional characterization. The analytical techniques used (WDXRF, XRD and FTIR) highlighted, on the one hand, the B form for [...] Read more.
This paper presents the synthesis of the triple substituted carbonated hydroxyapatite with magnesium, strontium and zinc (Mg-Sr-Zn-CHAp), as well as its structural, morphological and compositional characterization. The analytical techniques used (WDXRF, XRD and FTIR) highlighted, on the one hand, the B form for the apatite structure, as well as the presence of the three metal ions in the apatite structure, on the other hand (small shifts of 1120–900 cm−1 and 500–600 cm−1 absorption peaks due to the metals incorporated into the CHAp structure). The ratio between the metallic ions that substitute calcium and Ca2+, and phosphorus is increased, the value being 2.11 in comparison with CHAp and pure hydroxyapatite. Also, by using imaging techniques such as optical microscopy and SEM, spherical nanometric particles (between 150 and 250 nm) with a large surface area and large pores (6 m2/g surface area, pores with 6.903 nm diameters and 0.01035 cm3/g medium volume, determined by nitrogen adsorption/desorption analysis) and a pronounced tendency of agglomeration was highlighted. Also, the triple substituted carbonated hydroxyapatite was tested as an inorganic consolidant by using stone specimens prepared in the laboratory. The efficiency of Mg-Sr-Zn-CHAp in the consolidation processes was demonstrated by specific tests in the field: water absorption, peeling, freeze–thaw behavior, chromatic parameters as well as mechanical strength. All these tests presented conclusive values for the use of this consolidant in the consolidation procedures of stone surfaces (lower water absorption, increased mechanical strength, higher consolidation percent, decreased degradation rate by freeze–thaw, no significant color changes). Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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15 pages, 2287 KiB  
Article
Molecular Simulation of CO2 and H2 Encapsulation in a Nanoscale Porous Liquid
by Pablo Collado, Manuel M. Piñeiro and Martín Pérez-Rodríguez
Nanomaterials 2023, 13(3), 409; https://doi.org/10.3390/nano13030409 - 19 Jan 2023
Cited by 5 | Viewed by 2578
Abstract
In this study we analyse from a theoretical perspective the encapsulation of both gaseous H2 and CO2 at different conditions of pressure and temperature in a Type II porous liquid, composed by nanometric scale cryptophane-111 molecules dispersed in dichloromethane, using atomistic [...] Read more.
In this study we analyse from a theoretical perspective the encapsulation of both gaseous H2 and CO2 at different conditions of pressure and temperature in a Type II porous liquid, composed by nanometric scale cryptophane-111 molecules dispersed in dichloromethane, using atomistic molecular dynamics. Gaseous H2 tends to occupy cryptophane–111’s cavities in the early stages of the simulation; however, a remarkably greater selectivity of CO2 adsorption can be seen in the course of the simulation. Calculations were performed at ambient conditions first, and then varying temperature and pressure, obtaining some insight about the different adsorption found in each case. An evaluation of the host molecule cavities accessible volume was also performed, based on the guest that occupies the pore. Finally, a discussion between the different intermolecular host–guest interactions is presented, justifying the different selectivity obtained in the molecular simulation calculations. From the results obtained, the feasibility of a renewable separation and storage method for CO2 using these nanometric scale porous liquids is pointed out. Full article
(This article belongs to the Section Theory and Simulation of Nanostructures)
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32 pages, 6261 KiB  
Article
Numerical Analysis of the Light Modulation by the Frustule of Gomphonema parvulum: The Role of Integrated Optical Components
by Mohamed Ghobara, Cathleen Oschatz, Peter Fratzl and Louisa Reissig
Nanomaterials 2023, 13(1), 113; https://doi.org/10.3390/nano13010113 - 26 Dec 2022
Cited by 6 | Viewed by 3524
Abstract
Siliceous diatom frustules present a huge variety of shapes and nanometric pore patterns. A better understanding of the light modulation by these frustules is required to determine whether or not they might have photobiological roles besides their possible utilization as building blocks in [...] Read more.
Siliceous diatom frustules present a huge variety of shapes and nanometric pore patterns. A better understanding of the light modulation by these frustules is required to determine whether or not they might have photobiological roles besides their possible utilization as building blocks in photonic applications. In this study, we propose a novel approach for analyzing the near-field light modulation by small pennate diatom frustules, utilizing the frustule of Gomphonema parvulum as a model. Numerical analysis was carried out for the wave propagation across selected 2D cross-sections in a statistically representative 3D model for the valve based on the finite element frequency domain method. The influences of light wavelength (vacuum wavelengths from 300 to 800 nm) and refractive index changes, as well as structural parameters, on the light modulation were investigated and compared to theoretical predictions when possible. The results showed complex interference patterns resulting from the overlay of different optical phenomena, which can be explained by the presence of a few integrated optical components in the valve. Moreover, studies on the complete frustule in an aqueous medium allow the discussion of its possible photobiological relevance. Furthermore, our results may enable the simple screening of unstudied pennate frustules for photonic applications. Full article
(This article belongs to the Special Issue Photonic Properties of Nanostructured Biomaterials)
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10 pages, 3662 KiB  
Article
Superparamagnetic-like Micrometric Single Crystalline Magnetite for Biomedical Application Synthesis and Characterization
by Marius Chirita, Adrian Bezergheanu, Corneliu Bazil Cizmas and Aurel Ercuta
Magnetochemistry 2023, 9(1), 5; https://doi.org/10.3390/magnetochemistry9010005 - 24 Dec 2022
Cited by 2 | Viewed by 2036
Abstract
Single-crystalline magnetite (Fe3O4) particles having a size beyond the nanometric range (1 µm to 50 µm) and showing high (close to the bulk value) saturation-specific magnetization (σs = 92 emu/g), were obtained by the hydrothermal decomposition of the [...] Read more.
Single-crystalline magnetite (Fe3O4) particles having a size beyond the nanometric range (1 µm to 50 µm) and showing high (close to the bulk value) saturation-specific magnetization (σs = 92 emu/g), were obtained by the hydrothermal decomposition of the Fe-EDTA complex. The very low values of the magnetic remanence (σr = 0.82 emu/g) and coercitivity (μoHc = 1.53 mT) observed at room temperature (RT) suggest a superparamagnetic-like behavior, which is quite remarkable for such micrometric magnetite particles. As confirmed by vibrating sample magnetometer (VSM)-based measurements, minor changes in their magnetic properties occur between RT and 5K. Scanning electron microscopy (SEM) has revealed a morphology consisting of a combination of non-porous octahedral- and dodecahedral-shaped particles, energy dispersive X-ray analysis (EDX) has indicated high elemental (Fe and O) purity, whereas X-ray diffraction (XRD) has confirmed a single crystal structure. The nitrogen adsorbtion–desorption isotherm and pore size distribution are presented for the magnetite sample. Thermomagnetic records under zero field-cooled (ZFC) and field-cooled (FC) conditions have revealed a thermal hysteresis of the Verwey transition.The Verwey point (TV) at which the major step of the phase transformation takes place is located around 132 K for heating and around 122 K for cooling. These microcrystals do not remain agglomerated when the polarizing field is removed, an essential requirement in biomedical applications is met. Full article
(This article belongs to the Special Issue Advances in Magnetic Nanocarrier for Biomedical Applications)
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17 pages, 4069 KiB  
Article
A Biodegradable Flexible Micro/Nano-Structured Porous Hemostatic Dental Sponge
by Simin Sharifi, Solmaz Maleki Dizaj, Elham Ahmadian, Alireza Karimpour, Abdollah Maleki, Mohammad Yousef Memar, Mohammad Ali Ghavimi, Elaheh Dalir Abdolahinia and Khang Wen Goh
Nanomaterials 2022, 12(19), 3436; https://doi.org/10.3390/nano12193436 - 30 Sep 2022
Cited by 15 | Viewed by 3785
Abstract
A biodegradable micro/nano-structured porous hemostatic gelatin-based sponge as a dentistry surgery foam was prepared using a freeze-drying method. In vitro function evaluation tests were performed to ensure its hemostatic effect. Biocompatibility tests were also performed to show the compatibility of the sponge on [...] Read more.
A biodegradable micro/nano-structured porous hemostatic gelatin-based sponge as a dentistry surgery foam was prepared using a freeze-drying method. In vitro function evaluation tests were performed to ensure its hemostatic effect. Biocompatibility tests were also performed to show the compatibility of the sponge on human fetal foreskin fibroblasts (HFFF2) cells and red blood cells (RBCs). Then, 10 patients who required the extraction of two teeth were selected, and after teeth extraction, for dressing, the produced sponge was placed in one of the extracavities while a commercial sponge was placed in the cavity in the other tooth as a control. The total weight of the absorbed blood in each group was compared. The results showed a porous structure with micrometric and nanometric pores, flexibility, a two-week range for degradation, and an ability to absorb blood 35 times its weight in vitro. The prepared sponge showed lower blood clotting times (BCTs) (243.33 ± 2.35 s) and a lower blood clotting index (BCI) (10.67 ± 0.004%) compared to two commercial sponges that displayed its ability for faster coagulation and good hemostatic function. It also had no toxic effects on the HFFF2 cells and RBCs. The clinical assessment showed a better ability of blood absorption for the produced sponge (p-value = 0.0015). The sponge is recommended for use in dental surgeries because of its outstanding abilities. Full article
(This article belongs to the Special Issue New Insights in Nanomaterials for Dental Diseases Management)
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14 pages, 2696 KiB  
Article
Atmosphere-Assisted FLASH Sintering of Nanometric Potassium Sodium Niobate
by Ricardo Serrazina, Luis Pereira, Paula M. Vilarinho and Ana M. Senos
Nanomaterials 2022, 12(19), 3415; https://doi.org/10.3390/nano12193415 - 29 Sep 2022
Cited by 6 | Viewed by 2118
Abstract
The request for extremely low-temperature and short-time sintering techniques has guided the development of alternative ceramic processing. Atmosphere-assisted FLASH sintering (AAFS) combines the direct use of electric power to packed powders with the engineering of operating atmosphere to allow low-temperature conduction. The AAFS [...] Read more.
The request for extremely low-temperature and short-time sintering techniques has guided the development of alternative ceramic processing. Atmosphere-assisted FLASH sintering (AAFS) combines the direct use of electric power to packed powders with the engineering of operating atmosphere to allow low-temperature conduction. The AAFS of nanometric Potassium Sodium Niobate, K0.5Na0.5NbO3, a lead-free piezoelectric, is of great interest to electronics technology to produce efficient, low-thermal-budget sensors, actuators and piezo harvesters, among others. Not previously studied, the role of different atmospheres for the decrease in FLASH temperature (TF) of KNN is presented in this work. Additionally, the effect of the humidity presence on the operating atmosphere and the role of the compact morphology undergoing FLASH are investigated. While the low partial pressure of oxygen (reducing atmospheres) allows the decrease of TF, limited densification is observed. It is shown that AAFS is responsible for a dramatic decrease in the operating temperature (T < 320 °C), while water is essential to allow appreciable densification. In addition, the particles/pores morphology on the green compact impacts the uniformity of AAFS densification. Full article
(This article belongs to the Special Issue Ceramics and Nanostructures for Energy Harvesting and Storage)
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16 pages, 4030 KiB  
Article
Powder 3D Printing of Bone Scaffolds with Uniform and Gradient Pore Sizes Using Cuttlebone-Derived Calcium Phosphate and Glass-Ceramic
by Francesca Cestari, Yuejiao Yang, Janka Wilbig, Jens Günster, Antonella Motta and Vincenzo M. Sglavo
Materials 2022, 15(15), 5139; https://doi.org/10.3390/ma15155139 - 24 Jul 2022
Cited by 9 | Viewed by 2916
Abstract
The pore geometry of bone scaffolds has a major impact on their cellular response; for this reason, 3D printing is an attractive technology for bone tissue engineering, as it allows for the full control and design of the porosity. Calcium phosphate materials synthesized [...] Read more.
The pore geometry of bone scaffolds has a major impact on their cellular response; for this reason, 3D printing is an attractive technology for bone tissue engineering, as it allows for the full control and design of the porosity. Calcium phosphate materials synthesized from natural sources have recently attracted a certain interest because of their similarity to natural bone, and they were found to show better bioactivity than synthetic compounds. Nevertheless, these materials are very challenging to be processed by 3D printing due to technological issues related to their nanometric size. In this work, bone scaffolds with different pore geometries, with a uniform size or with a size gradient, were fabricated by binder jetting 3D printing using a biphasic calcium phosphate (BCP) nanopowder derived from cuttlebones. To do so, the nanopowder was mixed with a glass-ceramic powder with a larger particle size (45–100 µm) in 1:10 weight proportions. Pure AP40mod scaffolds were also printed. The sintered scaffolds were shown to be composed mainly by hydroxyapatite (HA) and wollastonite, with the amount of HA being larger when the nanopowder was added because BCP transforms into HA during sintering at 1150 °C. The addition of bio-derived powder increases the porosity from 60% to 70%, with this indicating that the nanoparticles slow down the glass-ceramic densification. Human mesenchymal stem cells were seeded on the scaffolds to test the bioactivity in vitro. The cells’ number and metabolic activity were analyzed after 3, 5 and 10 days of culturing. The cellular behavior was found to be very similar for samples with different pore geometries and compositions. However, while the cell number was constantly increasing, the metabolic activity on the scaffolds with gradient pores and cuttlebone-derived powder decreased over time, which might be a sign of cell differentiation. Generally, all scaffolds promoted fast cell adhesion and proliferation, which were found to penetrate and colonize the 3D porous structure. Full article
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12 pages, 2528 KiB  
Article
Time Estimation of Polymer Translocation through Nano-Membrane
by Maria-Alexandra Paun, Vladimir-Alexandru Paun and Viorel-Puiu Paun
Polymers 2022, 14(10), 2090; https://doi.org/10.3390/polym14102090 - 20 May 2022
Cited by 1 | Viewed by 2039
Abstract
In this paper, the charged polymer escapement phenomenon, via a little hole of nano-metric dimensions arranged in a constitutive biological membrane, is studied. We will present the case of the transport process of an ideal polymer in a 3-dimensional extended region separated by [...] Read more.
In this paper, the charged polymer escapement phenomenon, via a little hole of nano-metric dimensions arranged in a constitutive biological membrane, is studied. We will present the case of the transport process of an ideal polymer in a 3-dimensional extended region separated by a fine boundary named membrane in a free energy barrier attendance. Additionally, the general translocation time formula, respectively, the transition time from the cis area to the trans area, is presented. The model for estimation of the likelihood, designated by P(x, t), as a macromolecular chain of lengthiness equal to x, to be able to pass by the nanopore in escape period t, was optimized. The longest-lasting likely escape time found with this model is indicated to be tp = 330 μs. Thus, the results obtained with the described formula are in good agreement with those announced in the specialized literature. Full article
(This article belongs to the Special Issue Transport Processes of Polymers through Nanometric Pore Membranes)
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