Materials

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10 pages, 6298 KiB

Open AccessArticle

Synthesis and Characterization of Electrospun Carbon Nanofibers from Polyacrylonitrile and Graphite Nanoplatelets

by Hani Manssor Albetran

Materials 2023, 16(4), 1749; https://doi.org/10.3390/ma16041749 - 20 Feb 2023

Cited by 2 | Viewed by 1764

Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and [...] Read more.

Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffractometry (XRD) were used to characterize the synthesized ECNFs. The smooth ECNFs with a diameter of 129 ± 43 nm comprised conical platelets of 30–200 µm length. The plane-layered nanofibers contained crystallites along the long fiber axis and were mainly parallel. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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13 pages, 2222 KiB

Open AccessArticle

Modeling the Nonlinear Deformation of Highly Porous Cellular Plastics Filled with Clay Nanoplatelets

by Aivars Lagzdiņš, Alberts Zilaucs, Ilze Beverte and Jānis Andersons

Materials 2022, 15(3), 1033; https://doi.org/10.3390/ma15031033 - 28 Jan 2022

Cited by 1 | Viewed by 2197

Abstract

Rigid low-density plastic foams subjected to mechanical loads typically exhibit a nonlinear deformation stage preceding failure. At moderate strains, when the geometrical nonlinearity is negligible, such foam response is predominantly caused by the nonlinearity of deformation of their principal structural elements—foam struts. Orientational [...] Read more.

Rigid low-density plastic foams subjected to mechanical loads typically exhibit a nonlinear deformation stage preceding failure. At moderate strains, when the geometrical nonlinearity is negligible, such foam response is predominantly caused by the nonlinearity of deformation of their principal structural elements—foam struts. Orientational averaging of stresses in foam struts enables estimation of the stresses taken up by foams at a given applied strain. Based on a structural model of highly porous anisotropic cellular plastics filled with clay nanoplatelets and the orientational averaging, a method for calculating their nonlinear deformation is derived in terms of structural parameters of the porous material, the mechanical properties of the monolithic polymer, and filler particles and their spatial orientation. The method is applied to predicting the tensile stress-strain diagrams of organoclay-filled low-density rigid polyurethane foams, and reasonable agreement with experimental data is demonstrated. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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19 pages, 4811 KiB

Open AccessArticle

Bioconjugation Strategy for Ceramic Membranes Decorated with Candida Antarctica Lipase B—Impact of Immobilization Process on Material Features

by Joanna Kujawa, Marta Głodek, Izabela Koter, Guoqiang Li, Katarzyna Knozowska and Wojciech Kujawski

Materials 2022, 15(2), 671; https://doi.org/10.3390/ma15020671 - 17 Jan 2022

Cited by 5 | Viewed by 2286

Abstract

A strategy for the bioconjugation of the enzyme Candida antarctica lipase B onto titania ceramic membranes with varied pore sizes (15, 50, 150, and 300 kDa) was successfully performed. The relationship between the membrane morphology, i.e.,the pore size of the ceramic support, and [...] Read more.

A strategy for the bioconjugation of the enzyme Candida antarctica lipase B onto titania ceramic membranes with varied pore sizes (15, 50, 150, and 300 kDa) was successfully performed. The relationship between the membrane morphology, i.e.,the pore size of the ceramic support, and bioconjugation performance was considered. Owing to the dimension of the enzyme (~33 kDa), the morphology of the ceramics allowed (50, 150, and 300 kDa) or did not allow (15 kDa) the entrance of the enzyme molecules into the porous structure. Such a strategy made it possible to better understand the changes in the material (morphology) and physicochemical features (wettability, adhesiveness, and surface charge) of the samples, which were systematically examined. The silane functionalization and enzyme immobilization were accomplished via the covalent route. The samples were characterized after each stage of the modification, which was very informative from the material point of view. As a consequence of the modification, significant changes in the contact angle, roughness, adhesion, and zeta potential were observed. For instance, for the 50 kDa membrane, the contact angle increased from 29.1 ± 1.5° for the pristine sample to 72.3 ± 1.5° after silane attachment; subsequently, it was reduced to 57.2 ± 1.5° after the enzyme immobilization. Finally, the contact angle of the bioconjugated membrane used in the enzymatic process rose to 92.9 ± 1.5°. By roughness (S_q) controlling, the following amendments were noticed: for the pristine 50 kDa membrane, S_q = 1.87 ± 0.21 µm; after silanization, S_q = 2.33 ± 0.30 µm; after enzyme immobilization, S_q = 2.74 ± 0.26 µm; and eventually, after the enzymatic process, S_q = 2.37 ± 0.27 µm. The adhesion work of the 50 kDa samples was equal to 136.41 ± 2.20 mN m⁻¹ (pristine membrane), 94.93 ± 2.00 mN m⁻¹ (with silane), 112.24 ± 1.90 mN m⁻¹ (with silane and enzyme), and finally, 69.12 ± 1.40 mN m⁻¹ (after the enzymatic process). The materials and physicochemical features changed substantially, particularly after the application of the membrane in the enzymatic process. Moreover, the impact of ceramic material morphology on the zeta potential value is here presented for the first time. With an increase in the ceramic support cut-off, the amount of immobilized lipase rose, but the specific productivity was higher for membranes possessing smaller pores, owing to the higher grafting density. For the enzymatic process, two modes of accomplishment were selected, i.e., stirred-tank and cross-flow. The latter method was characterized by a much higher effectiveness, with a resulting productivity equal to 99.7 and 60.3 µmol h⁻¹ for the 300 and 15 kD membranes, respectively. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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20 pages, 36486 KiB

Open AccessArticle

Effect of Polymer Additives on the Microstructure and Mechanical Properties of Self-Leveling Rubberised Concrete

by Weronika Kujawa, Iwona Tarach, Ewa Olewnik-Kruszkowska and Anna Rudawska

Materials 2022, 15(1), 249; https://doi.org/10.3390/ma15010249 - 29 Dec 2021

Cited by 4 | Viewed by 2341

Abstract

The materials based on concrete with an addition of rubber are well-known. The interaction between concrete components and rubber particles is in the majority cases insufficient. For this reason, different substances are introduced into concrete-rubber systems. The aim of this paper is to [...] Read more.

The materials based on concrete with an addition of rubber are well-known. The interaction between concrete components and rubber particles is in the majority cases insufficient. For this reason, different substances are introduced into concrete-rubber systems. The aim of this paper is to establish the influence of five different polymer additives, i.e., 1. an aqueous dispersion of a styrene-acrylic ester copolymer (silanised) (ASS), 2. water dispersion of styrene-acrylic copolymer (AS), 3. anionic copolymer of acrylic acid ester and styrene in the form of powder (AS.RDP), 4. water polymer dispersion produced from the vinyl acetate and ethylene monomers (EVA), 5. copolymer powder of vinyl acetate and ethylene (EVA.RDP)) on the properties of the self-leveling rubberised concrete. Scanning electron microscopy has allowed to establish the interaction between the cement paste and rubber aggregates. Moreover, the compressive strength and flexural strength of the studied materials were evaluated. The results indicate that the mechanical properties depend extensively on the type as well as the amount of the polymer additive introduced into the system. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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17 pages, 531 KiB

Open AccessArticle

Chasing the Critical Wetting Transition. An Effective Interface Potential Method

by Paweł Bryk and Artur P. Terzyk

Materials 2021, 14(23), 7138; https://doi.org/10.3390/ma14237138 - 24 Nov 2021

Cited by 3 | Viewed by 1674

Abstract

Wettablity is one of the important characteristics defining a given surface. Here we show that the effective interface potential method of determining the wetting temperature, originally proposed by MacDowell and Müller for the surfaces exhibiting the first order wetting transition, can also be [...] Read more.

Wettablity is one of the important characteristics defining a given surface. Here we show that the effective interface potential method of determining the wetting temperature, originally proposed by MacDowell and Müller for the surfaces exhibiting the first order wetting transition, can also be used to estimate the wetting temperature of the second order (continuous) wetting transition. Some selected other methods of determination of the wetting temperature are also discussed. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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20 pages, 36910 KiB

Open AccessArticle

Fluorescent Chitosan Modified with Heterocyclic Aromatic Dyes

by Halina Kaczmarek, Agnieszka Tafelska-Kaczmarek, Katarzyna Roszek, Joanna Czarnecka, Beata Jędrzejewska and Katarzyna Zblewska

Materials 2021, 14(21), 6429; https://doi.org/10.3390/ma14216429 - 26 Oct 2021

Cited by 5 | Viewed by 2351

Abstract

Chitosan is a valuable, functional, and biodegradable polysaccharide that can be modified to expand its applications. This work aimed to obtain chitosan derivatives with fluorescent properties. Three heterocyclic aromatic dyes (based on benzimidazole, benzoxazole, and benzothiazole) were synthesized and used for the chemical [...] Read more.

Chitosan is a valuable, functional, and biodegradable polysaccharide that can be modified to expand its applications. This work aimed to obtain chitosan derivatives with fluorescent properties. Three heterocyclic aromatic dyes (based on benzimidazole, benzoxazole, and benzothiazole) were synthesized and used for the chemical modification of chitosan. Emission spectroscopy revealed the strong fluorescent properties of the obtained chitosan derivatives even at a low N-substitution degree of the dye. The effect of high-energy ultraviolet radiation (UV–C) on modified chitosan samples was studied in solution with UV–Vis spectroscopy and in the solid state with FTIR spectroscopy. Moreover, cytotoxicity towards three different cell types was evaluated to estimate the possibilities of biomedical applications of such fluorescent chitosan-based materials. It was found that the three new derivatives of chitosan were characterized by good resistance to UV–C, which suggests the possibility of using these materials in medicine and various industrial sectors. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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11 pages, 3557 KiB

Open AccessArticle

Laser Heating Study of the High-Temperature Interactions in Nanograined Uranium Carbides

by Sanjib Chowdhury, Dario Manara, Oliver Dieste-Blanco, Davide Robba and António Pereira Gonçalves

Materials 2021, 14(19), 5568; https://doi.org/10.3390/ma14195568 - 25 Sep 2021

Cited by 2 | Viewed by 1768

Abstract

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect [...] Read more.

Nanograined nuclear materials are expected to have a better performance as spallation targets and nuclear fuels than conventional materials, but many basic properties of these materials are still unknown. The present work aims to contribute to their better understanding by studying the effect of grain size on the melting and solid–solid transitions of nanograined UC_2−y. We laser-heated 4 nm–10 nm grain size samples with UC_2−y as the main phase (but containing graphite and UO₂ as impurities) under inert gas to temperatures above 3000 K, and their behavior was studied by thermal radiance spectroscopy. The UC_2−y solidification point (2713(30) K) and α-UC₂ to β-UC₂ solid–solid transition temperature (2038(10) K) were observed to remain unchanged when compared to bulk crystalline materials with micrometer grain sizes. After melting, the composite grain size persisted at the nanoscale, from around 10 nm to 20 nm, pointing to an effective role of carbon in preventing the rapid diffusion of uranium and grain growth. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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11 pages, 3126 KiB

Open AccessArticle

Insight into the Mechanisms of Low Coverage Adsorption of N-Alcohols on Single Walled Carbon Nanohorn

by Grzegorz Stanisław Szymański, Anna Kaczmarek-Kędziera, Monika Zięba, Piotr Kowalczyk and Artur Piotr Terzyk

Materials 2021, 14(14), 4001; https://doi.org/10.3390/ma14144001 - 17 Jul 2021

Cited by 2 | Viewed by 1904

Abstract

We report for the first time the chromatographic study of n-alcohols (from methanol to butanol) adsorption on single walled carbon nanohorn (SWCNH). Using measured temperature dependence of adsorption isotherms (373–433 K) the isosteric adsorption enthalpy is calculated and compared with the data reported [...] Read more.

We report for the first time the chromatographic study of n-alcohols (from methanol to butanol) adsorption on single walled carbon nanohorn (SWCNH). Using measured temperature dependence of adsorption isotherms (373–433 K) the isosteric adsorption enthalpy is calculated and compared with the data reported for a graphite surface. It is concluded that a graphite surface is more homogeneous, and the enthalpy of adsorption on SWCNHs at zero coverage correlates well with molecular diameter and polarizability, suggesting leading role of dispersive interactions, i.e., no heteroatoms presence in the walls of SWCNH structures. Next using modern DFT approach we calculate the energy of n-alcohols interactions with a graphene sheet and with a single nanocone finally proposing a more realistic—double nanocone model. Obtained results suggest alcohols entrapping between SWCNH with OH groups located toward nanocones ends, leading to the conclusions about very promising future applications of SWCNHs in catalytic reactions with participation of n-alcohols. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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17 pages, 2591 KiB

Open AccessArticle

Thin Film Mixed Matrix Hollow Fiber Membrane Fabricated by Incorporation of Amine Functionalized Metal-Organic Framework for CO₂/N₂ Separation

by Guoqiang Li, Wojciech Kujawski, Katarzyna Knozowska and Joanna Kujawa

Materials 2021, 14(12), 3366; https://doi.org/10.3390/ma14123366 - 17 Jun 2021

Cited by 23 | Viewed by 3272

Abstract

Membrane separation technology can used to capture carbon dioxide from flue gas. However, plenty of research has been focused on the flat sheet mixed matrix membrane rather than the mixed matrix thin film hollow fiber membranes. In this work, mixed matrix thin film [...] Read more.

Membrane separation technology can used to capture carbon dioxide from flue gas. However, plenty of research has been focused on the flat sheet mixed matrix membrane rather than the mixed matrix thin film hollow fiber membranes. In this work, mixed matrix thin film hollow fiber membranes were fabricated by incorporating amine functionalized UiO-66 nanoparticles into the Pebax^® 2533 thin selective layer on the polypropylene (PP) hollow fiber supports via dip-coating process. The attenuated total reflection-Fourier transform infrared (ATR-FTIR), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) mapping analysis, and thermal analysis (TGA-DTA) were used to characterize the synthesized UiO-66-NH₂ nanoparticles. The morphology, surface chemistry, and the gas separation performance of the fabricated Pebax^® 2533-UiO-66-NH₂/PP mixed matrix thin film hollow fiber membranes were characterized by using SEM, ATR-FTIR, and gas permeance measurements, respectively. It was found that the surface morphology of the prepared membranes was influenced by the incorporation of UiO-66 nanoparticles. The CO₂ permeance increased along with an increase of UiO-66 nanoparticles content in the prepared membranes, while the CO₂/N₂ ideal gas selectively firstly increased then decreased due to the aggregation of UiO-66 nanoparticles. The Pebax^® 2533-UiO-66-NH₂/PP mixed matrix thin film hollow fiber membranes containing 10 wt% UiO-66 nanoparticles exhibited the CO₂ permeance of 26 GPU and CO₂/N₂ selectivity of 37. Full article

(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)

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