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The time-evolution of dynamics as well as microstructure and mechanical response of phosphate-based geopolymers was probed using x-ray photon correlation spectroscopy and rheological tests. The analyzed relaxation processes in the freshly prepared geopolymer mixes evidenced a q-independent mode of the autocorrelation function, ascribed to density fluctuations of the already established molecular network, undergoing reconfiguration without significant mass transport. Upon curing, the detected motions are localized and depict a system evolving toward structural arrest dominated by slower hyperdiffusive dynamics, characterized by a compressed exponential regime, pointing to a structural relaxation process subjected to internal stresses, in a context of marked dynamical and structural heterogeneity. The system ages through a "densification" process producing declining small angle scattered intensity, as two finely intermixed gel-like reaction products, namely, one hydrated aluminophosphate and one hydrated silica, form a percolated network possessing surface fractal scaling of progressively shorter average correlation length. In this scenario, the nominal Al/P molar ratio of the mix, being an index of network-forming ability, is positively correlated with the dynamic viscosity and the overall kinetics, whereas the contrary occurs for the fraction of water. [ABSTRACT FROM AUTHOR]

Plastics represent an integral part of our everyday lives, with various functions from packaging materials to insulation layers in our buildings. Pure expanded polystyrene (EPS) is a good example of a fully recyclable material. However, once polluted with other materials or substances, EPS becomes a serious environmental burden. In this work, waste EPS for the production of greener building composites with balanced properties and utility value was investigated. Natural aggregate (2/4 mm) was substituted with corresponding fractions of a thermoplastic alternative in portions of 25, 50, 75, and 100 vol.%. The comprehensive experimental investigation evaluated physical and mechanical properties, heat transport and accumulation, and water absorption characteristics. Due to the uniformly distributed plastic particles in the hardened cement-based matrix, the data revealed an important reduction in the dead weight of produced mortars, which also reduced thermal conductivity by up to 47%. On one hand, lightweight mortars showed partially reduced mechanical resistivity; on the other hand, the EPS bead-modified structure turned out to be effective in liquid water transport reduction. [ABSTRACT FROM AUTHOR]

This work aims to characterize 3D-printed structures composed of a thermoplastic material (polylactic acid (PLA)) containing a combination of magnetic particles composed of iron(III) oxide (hematite) and iron(II)–iron (III) oxide (magnetite) with various infill densities and print orientations in regard to their possible processing by Fused Filament Fabrication additive technology. The correct processing temperatures have been determined using thermal analysis, and the paramagnetic and mechanical properties of the samples have been tested. The relative permeability has been identified to be strongly dependent on the topology parameters of the tested samples. The results of the inductance values for the samples without magnetic additives (infill densities 50% and 100%) have been detected to be comparable; nonetheless, the magnetic samples with 100% infill density has been found to be about 50% higher. A similar trend has been observed in the case of the values of the relative permeability, where the magnetic samples with 100% infill density have been measured as having an about 40% increased relative permeability in the comparison with the samples without magnetic additives (infill densities 20–100%). Finite Element Modelling (FEM) simulations have been applied to determine the magnetic field distributions and, moreover, to calculate the holding forces of all the printed samples. The maximum value of the holding force for the minimum distance of the plastic plate has been found to reach a value of almost 300 N (magnetic sample with 100% infill density). The obtained comprehensive characterization of the printed samples may be utilized for designing and tuning the desired properties of the samples needed in various industrial applications. [ABSTRACT FROM AUTHOR]

Membrane chemistry belongs to the field in which 3D printing can advantageously also be used because of enabling the production of prototypes with precisely defined dimensions. The presented work aimed to develop new polymeric compositions for heterogeneous cation exchange membranes manufactured using stereolithography (SLA) from commercially available materials. Three types of photo‐curable thermoset resins (acrylic resin and two types of epoxy resins) were used as polymer matrixes in combination with strong acid cation exchange resin (CER) powder. The membrane production consisted of several stages, namely mixing the photo‐curable resin with finely ground CER powder, processing using SLA, and appropriate post‐curing using UV light and elevated temperature. The work aimed to monitor the influence of the photo‐curable resin type and post‐curing on the microstructural, electrochemical, and mechanical properties of resulting membrane objects. The results revealed that heterogeneous cation exchange membranes could be processed using SLA from the mixture of the acrylic photo‐curable resin and CER powder (weight ratio of 60/40) without the need for post‐curing. These products exhibited high permselectivity (93%), high ion exchange capacity (2.23 meq⋅g−1), and sufficiently low electrical resistance (2200 Ω⋅cm), which predetermines them for efficient electrophoretic separation. [ABSTRACT FROM AUTHOR]

Traditional supplementary cementitious materials (SCMs) have been proven to reduce the negative impact of Portland cement production on the environment. However, the availability of SCMs becomes limited due to their extensive usage. For this reason, our work aimed to investigate the effect of partial substitution of ordinary Portland cement (OPC) with two different types of carbon-rich waste powders—biochar (BC) and coal dust (CD), dosed separately up to 10 wt.% of OPC, on the physical, microstructural and mechanical properties of hardened specimens. Obtained data pointed out that replacing OPC with small amounts of BC and CD (not exceeding 5.0 wt.% and 2.5% wt.%, respectively) initiated an increment in mechanical strengths due to a decrease in total open porosity and enhanced formation of hydration products of such composites compared with the reference. Overall, both examined alternatives, if added in appropriate amounts, have the perspective to be effectively applied in cement manufacturing and concrete production, and thus to importantly contribute to the long-term sustainability of the construction industry in view of energy savings, reduced releasing of the greenhouse gasses and mitigating of global climate changes. [ABSTRACT FROM AUTHOR]

This work aims to characterize printing structures with various infill densities composed of a thermoplastic material containing magnetic particles composed of mainly Iron(III) oxides with regard to their possible processing with the additive technology of Fused Filament Fabrication. A polyethylene terephthalate glycol (PET-G) structural thermoplastic with the addition of Iron(III)) oxides has been selected, and correct processing temperatures have been determined using thermal analysis. The paramagnetic properties of printed products consisting of different filling densities have been tested. Relative permeability has been identified to be strongly dependent on the printed internal structures of tested products. The samples composed of the densest structure have shown relative permeability higher by 18% with respect to the sample printed with the least dense structure. Finite Element Modelling (FEM) simulations have been applied to determine magnetic field distributions and, moreover, to calculate the holding forces of all printed samples. The performed simulations confirmed that produced composites might be utilized as magnetic switches and sensors or as more advanced components for homogenizing electric motors' magnetic fields. Moreover, magnetic properties might be tuned according to the specific needs printing structure with the suitable density. [ABSTRACT FROM AUTHOR]

3D printing, also known as additive manufacturing, is becoming increasingly popular for prototype processing in industrial practice. Laser sintering, which is a laser powder bed fusion technique, is a versatile and common 3D printing technology, which enables compact and high-quality products. Polyamide 12, a popular 3D printing material, provides reliable mechanical and thermal properties. Weaknesses in applying this technology for polyamide 12 include incomplete information regarding the application of various types of additives and different printing orientations with respect to the properties. This study aimed to investigate the influence of various additives (including carbon fiber, glass fiber, flame retardant, and aluminum powder) combined with polyamide 12, using processing of predefined powder refreshing mixture on the properties of a finished product. The thermal, surface, and mechanical properties of samples printed with five different polyamides 12-based powders at three different print orientations were investigated. It was found that the inclusion of additives decreases the tensile strength and increases the surface roughness of printed components—however, the toughness increases. The results can assist designers in selecting an appropriate material that will produce a finished part with the required properties for a given application. [ABSTRACT FROM AUTHOR]

The process of obtaining chemically bonded phosphate ceramics generally involves the use of metallic oxides, the preparation of which consumes high quantities of energy. The present study proposes a method to recycle slags generated by a steel production process that is widely used across the world—the electric arc furnace. A chemically bonded phosphate ceramic is produced by exploiting the high content of metals present in the slag, realizing the conditions to mitigate the environmental impact of the industrial by-product. In situ infrared spectroscopy, isothermal conduction calorimetry, and X-ray diffraction revealed that the setting reaction involves the formation of amorphous products in the form of metallic phosphate hydrates and a fraction of calcium silicate hydrates similar to those found in portland cement. This phosphate matrix allows the effective immobilization of heavy metals in the slag, such as Cr and As. According to the results of mechanical tests, which showed compression resistance of 15–25 MPa , and leaching tests, slag-based phosphate cement can be used without restrictions as a construction material for applications such as mortars or bricks. [ABSTRACT FROM AUTHOR]

One-sided surface charred European beech wood (Fagus sylvatica L.) was studied. Radial and tangential specimens of dimensions of 50 × 25 × 350 mm were one-sided surface charred at 200, 250, 300, 350, and 400 °C for various times using a contact heating system. Specimens of dimensions of 50 × 25 × 50 mm3 were prepared for treatment intensity analysis and its effect on surface wettability. Density profiles of the radial and tangential charred specimens were determined using X-ray densitography with a resolution of 0.05 mm. The wettability of the one-sided surface charred wood specimens was analyzed via contact angle, measured using the sessile drop method and determined over 10 to 150 s. The oven-dried specimens were partially submerged in water and water uptake was recorded after 2, 4, 6, 8, 10, 48, and 72 h according to EN-927-5. The surface density of the radial specimen groups charred at 200 °C for 6 min and 250 °C for 4 min decreased by about 4.5 to 8.2%. With increasingly severe charring, the surface density decreased by about 15.5 to 33.5%. A mild charring process produced a surface charred layer of approx. 2 mm, while higher temperatures and longer times affected the density up to 4–6 mm beneath the surface. Differences were found between the water uptake of the radial and tangential charred beech specimens. The most significant decrease of 56% in water uptake was recorded for the radial group prepared at 200 °C for 20 min after floating in water for 72 h. Water uptake in the radial groups modified at 250 °C for 4 and 6 min after 72 h decreased by 38% and 36%, respectively. The tangential groups did not show any statistically significant decrease. The average water uptake of the groups charred at 200 °C for 20 min, 350 °C for 2 min and 400 °C for 1 min was greater than that of the reference; the variability of the measured data was significantly greater due to the highly anisotropic character of the tangential specimens. Micro cracks were also visible on the surface. Concluding from the results of this study, one-sided surface charred beech wood exhibits increased potential in terms of wood–water related properties when a temperature range of 200–400 °C is applied. [ABSTRACT FROM AUTHOR]

Effect of the shape of 3D printed samples on fire behavior of polyethylene terephthalate glycol (PET‐G) and PET‐G additivated with a mix of aluminum hypophosphite (AHP) and melamine cyanurate as flame retardant, was investigated. The additives improved fire performance (e.g., maximum average rate of heat emission, total oxygen consumption, heat release rate indices) irrespective of structural complexity, favoring carbonaceous char formation. However, at increasing structural complexity, they promoted higher release of smoke, compared to neat PET‐G, because of a change in the prevalent retardation mechanism, which became dominated by the flame inhibition action of AHP. Consequently, the synergistic effect obtained combining the two additives, was hindered. Impact of product design on mechanisms of fire retardation helps in devising engineering solutions aimed at meeting required level of fire‐safety performance, which should be tailored to the specific product. [ABSTRACT FROM AUTHOR]

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In this study, the spinnability of styrene–ethyl acrylate copolymers prepared via emulsion polymerization was explored with the aim to establish the influence of glass transition temperature and polymer composition on morphological features of electrospun materials with regard to their hydrophobic/hydrophilic nature. Nonwoven mats from polymer solutions inN,N′-dimethylformamide were spun using the electrospinning method (Nanospider™ device). It was demonstrated that changing the copolymer polarity and glass transition temperature by copolymer composition or utilizing different supporting materials might lead to nanofiber webs with controlled hydrophobic/hydrophilic properties, which predetermines them for a wide range of applications such as protective textiles, composites, etc. [ABSTRACT FROM PUBLISHER]

Nowadays, additive manufacturing—also called 3D printing—represents a well-established technology in the field of the processing of various types of materials manufacturing products used in many industrial sectors. The most common type of 3D printing uses the fused filament fabrication (FFF) method, in which materials based on thermoplastics or elastomers are processed into filaments. Much effort was dedicated to improving the properties and processing of such printed filaments, and various types of inorganic and organic additives have been found to play a beneficial role. One of them, calcium carbonate (CaCO3), is standardly used as filler for the processing of polymeric materials. However, it is well-known from its different applications that CaCO3 crystals may represent particles of different morphologies and shapes that may have a crucial impact on the final properties of the resulting products. For this reason, three different synthetic polymorphs of CaCO3 (aragonite, calcite, and vaterite) and commercially available calcite powders were applied as fillers for the fabrication of polymeric filaments. Analysis of obtained data from different testing techniques has shown significant influence of filament properties depending on the type of applied CaCO3 polymorph. Aragonite particles showed a beneficial impact on the mechanical properties of produced filaments. The obtained results may help to fabricate products with enhanced properties using 3D printing FFF technology. [ABSTRACT FROM AUTHOR]

Most of the historical and old building stock in Europe are constructed from masonry, when brick, stones, or their combination are bound with traditional mortars. Rising damp, due to accompanying effects, is the main factor influencing the quality of indoor climate as well as having an important impact on the durability of masonry structures. In this study, new types of lightweight concrete with waste aggregate content as a suitable material for remediation of damp damaged masonries were designed and tested. Alternative aggregate served as silica sand substitution in the range of 0–100 vol.%. Basic structural properties, mechanical resistance, water, and water vapor transport properties were measured after 28 days of water curing and were compared with dense reference concrete and with traditional masonry materials as well. Moreover, the porous structure of produced concretes and changes caused by usage of alternative aggregate usage were evaluated with the mercury intrusion porosimetry (MIP) technique. Obtained experimental data showed the suitability of modified concretes with 25–50 vol.% of waste aggregate content to ensure acceptable strength and hydric properties, and these properties were found to be comparable with masonry structures and materials used in the past. [ABSTRACT FROM AUTHOR]

The aim of this paper was to analyze selected properties of beech wood (Fagus sylvatica L.) treated by one-sided surface charring. Specimens were one-side charred with a hot plate using several time-temperature combinations (from 200 to 400 °C). Characteristics such as colour, discoloration, surface roughness, fire resistance, total carbohydrate content at several wood layers and decay resistance were evaluated. Surface charring was applied to the radial and tangential surfaces. Colour measurements showed that the surface of the wood turned grey due to charring. In addition to colour measurements, other experiments showed significant differences between radial and tangential specimens due to their different structures. The higher the temperature used in treating them, the lower the roughness values for radial specimens, while the trend for tangential specimens was the opposite. A smoother surface is more fire resistant, so radial specimens are generally better in this regard. Tangential specimens are more susceptible during preparation to forming cracks that impair flame resistance because a continuous protective densified layer is not formed. The determination of total carbohydrates revealed significant changes at various wood depths after surface charring. These changes were more predictable in radial specimens due to the annual ring orientation, because each layer consisted of a similar earlywood/latewood ratio. Finally, when decay resistance was assessed, weight loss was found to be lower in all specimens than in the references. The results suggest that charring at a particular combination of temperature and time improved the investigated properties of the surface-modified beech. [ABSTRACT FROM AUTHOR]

This paper focuses on the preparation of two types of hydrophobic nanolayers using electrospinning technology. The first synthetic approach consists in direct fiberizing of polymeric phenyl-methyl-polyphosphazene Ph-Me(p) with the aim to preparing nanolayers that have significant hydrophobicity and thermal stability. The preparation of Ph-Me(p) is a multi-step reaction which produces a relatively low amount of the product. The second area of our interest was the creation of nanofibers formed from a mixture of some commercially available organic polymers and a cyclo -phosphazene derivative. In this case, tri(phenyl)-trimethyl- cyclo -triphosphazene, Ph-Me(t), whose synthesis is less complicated than its polymeric form, was used as an additive. The influence of the Ph-Me(t) additive in the nanofibers on the affinity to water was compared with the affinity of nanolayers made from a pure commercial polymer, i.e. without any phosphazene additive. It was also shown that the hydrophobic properties of fibers formed from Ph-Me(p) dissolved especially in THF are better than those of the nanofibers composed of a commercial polymer with the addition of Ph-Me(t). [ABSTRACT FROM AUTHOR]