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Volume 13, February-1

Materials, Volume 13, Issue 4 (February-2 2020) – 213 articles

Cover Story (view full-size image): Poly(L-lactide-co-glycolide)-block-poly (ethylene oxide) copolymer modified by blending with grafted dextrin or maltodextrin demonstrate very useful feature of this material as a biodegradable polymeric matrix for controlled release system of herbicides. The modification PLAGA/PEG copolymer by blending with modified dextrin affects the improvement of the release profile of active agent via enhancement of susceptibility of polymeric carrier to enzymatic degradation. This type of degradation allowed for the leaching of tested herbicides into the soil within few months which is very required from agrochemical and environmental protection point of view, because active substances are released through the whole vegetation period of cultivated plants. View this paper.
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Open AccessFeature PaperArticle
A Modular Millifluidic Platform for the Synthesis of Iron Oxide Nanoparticles with Control over Dissolved Gas and Flow Configuration
Materials 2020, 13(4), 1019; https://doi.org/10.3390/ma13041019 - 25 Feb 2020
Cited by 7 | Viewed by 1439
Abstract
Gas–liquid reactions are poorly explored in the context of nanomaterials synthesis, despite evidence of significant effects of dissolved gas on nanoparticle properties. This applies to the aqueous synthesis of iron oxide nanoparticles, where gaseous reactants can influence reaction rate, particle size and crystal [...] Read more.
Gas–liquid reactions are poorly explored in the context of nanomaterials synthesis, despite evidence of significant effects of dissolved gas on nanoparticle properties. This applies to the aqueous synthesis of iron oxide nanoparticles, where gaseous reactants can influence reaction rate, particle size and crystal structure. Conventional batch reactors offer poor control of gas–liquid mass transfer due to lack of control on the gas–liquid interface and are often unsafe when used at high pressure. This work describes the design of a modular flow platform for the water-based synthesis of iron oxide nanoparticles through the oxidative hydrolysis of Fe2+ salts, targeting magnetic hyperthermia applications. Four different reactor systems were designed through the assembly of two modular units, allowing control over the type of gas dissolved in the solution, as well as the flow pattern within the reactor (single-phase and liquid–liquid two-phase flow). The two modular units consisted of a coiled millireactor and a tube-in-tube gas–liquid contactor. The straightforward pressurization of the system allows control over the concentration of gas dissolved in the reactive solution and the ability to operate the reactor at a temperature above the solvent boiling point. The variables controlled in the flow system (temperature, flow pattern and dissolved gaseous reactants) allowed full conversion of the iron precursor to magnetite/maghemite nanocrystals in just 3 min, as compared to several hours normally employed in batch. The single-phase configuration of the flow platform allowed the synthesis of particles with sizes between 26.5 nm (in the presence of carbon monoxide) and 34 nm. On the other hand, the liquid–liquid two-phase flow reactor showed possible evidence of interfacial absorption, leading to particles with different morphology compared to their batch counterpart. When exposed to an alternating magnetic field, the particles produced by the four flow systems showed ILP (intrinsic loss parameter) values between 1.2 and 2.7 nHm2/kg. Scale up by a factor of 5 of one of the configurations was also demonstrated. The scaled-up system led to the synthesis of nanoparticles of equivalent quality to those produced with the small-scale reactor system. The equivalence between the two systems is supported by a simple analysis of the transport phenomena in the small and large-scale setups. Full article
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Open AccessArticle
Influence of Monomer Ratios on Molecular Weight Properties and Dispersing Effectiveness in Polycarboxylate Superplasticizers
Materials 2020, 13(4), 1022; https://doi.org/10.3390/ma13041022 - 24 Feb 2020
Cited by 1 | Viewed by 828
Abstract
A series of polycarboxylate superplasticizer (PCE) polymers were synthesized from acrylic acid (AA) and isoprenyloxy polyethylene glycol ether (IPEG) at the mole ratios of 3.0, 4.2, 5.0 and 6.0. In this study, the molecular weight properties of PCE polymers were recorded by size [...] Read more.
A series of polycarboxylate superplasticizer (PCE) polymers were synthesized from acrylic acid (AA) and isoprenyloxy polyethylene glycol ether (IPEG) at the mole ratios of 3.0, 4.2, 5.0 and 6.0. In this study, the molecular weight properties of PCE polymers were recorded by size exclusion chromatography with the time interval of 1 h. Mini slump test was used to detect the dispersing effectiveness of PCE polymer in cement paste. The results indicated that the reaction rate of monomers, conversion of 52IPEG macromonomer and molecular weight of PCE polymers increased with the general adding ratio of AA to IPEG macromonomers while the side chain density of PCE polymers decreased. PCE polymers possessed molecular weight around 30,000 g/mol with low side chain density, and long main chain length presented high initial dispersing effectiveness at the low dosage around 0.12%. The majority of effective PCE polymers were formed during the adding period of acrylic acid in the first 3 h. Full article
(This article belongs to the Special Issue Polymer in/on Concrete)
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Open AccessArticle
Flexible Magnetic Polymer Composite Substrate with Ba1.5Sr1.5Z Hexaferrite Particles of VHF/Low UHF Patch Antennas for UAVs and Medical Implant Devices
Materials 2020, 13(4), 1021; https://doi.org/10.3390/ma13041021 - 24 Feb 2020
Viewed by 722
Abstract
Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε [...] Read more.
Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε), have attracted great attention, because they facilitate miniaturization of microwave devices while keeping or enhancing electromagnetic characteristics. Mechanically millled Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) hexaferrite particles were used to increase permeability in the interesting frequency band. The microwave properties of Ba1.5Sr1.5Z composites were predicted and measured. Hansen’s zero-order analysis of antenna bandwidth and electromagnetic field simulation showed that the hexaferrite-based flexible composite could enhance a bandwidth and achieve the miniaturization of antennas as well. The magnetic antenna substrates can be a good solution to integrate antennas into the UAVs whose dimensions are comparable to or larger than communication wavelength. Full article
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Open AccessArticle
Fractal Characteristics of Chip Morphology and Tool Wear in High-Speed Turning of Iron-Based Super Alloy
Materials 2020, 13(4), 1020; https://doi.org/10.3390/ma13041020 - 24 Feb 2020
Viewed by 786
Abstract
Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based [...] Read more.
Considering that iron-based super alloy is a kind of difficult-to-cut material, it is easy to produce work hardening and serious tool wear during machining. Therefore, this work aims to explore the chip change characteristics and tool wear mechanism during the processing of iron-based super alloy, calculate the fractal dimensions of chip morphology and tool wear morphology, and use fractals to analyze their change trend. Meanwhile, a new cutting tool with a super ZX coating is used for a high-speed dry turning experiment. The results indicate that the morphology of the chip is saw-tooth, and its color changes gradually, due to the oxidation reaction. The main wear mechanisms of the tool involve abrasive wear, adhesive wear, oxidation wear, coating spalling, microcracking and chipping. The fractal dimension of the tool wear surface and chip is increased with the improvement of cutting speed. This work investigates the fractal characteristics of chip morphology and tool wear morphology. The fractal dimension changes regularly with the change of tool wear, which plays an important role in predicting this tool wear. It is also provides some guidance for the efficient processing of an iron-based super alloy. Full article
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Open AccessArticle
The Impact of the Vanadium Oxide Addition on the Physicochemical Performance Stability and Intercalation of Lithium Ions of the TiO2-rGO-electrode in Lithium Ion Batteries
Materials 2020, 13(4), 1018; https://doi.org/10.3390/ma13041018 - 24 Feb 2020
Cited by 3 | Viewed by 676
Abstract
This work determines the effect of the addition of various amounts of vanadium oxide on the work of a cell built from a hybrid VxOy-TiO2-rGO system in a lithium-ion cell. Moreover, a new method based on solvothermal [...] Read more.
This work determines the effect of the addition of various amounts of vanadium oxide on the work of a cell built from a hybrid VxOy-TiO2-rGO system in a lithium-ion cell. Moreover, a new method based on solvothermal chemistry is proposed for the creation of a new type of composite material combining reduced graphene, vanadium oxide and crystalline anatase. The satisfactory electrochemical properties of VxOy-TiO2-rGO hybrids can be attributed to the perfect matching of the morphology and structure of VxOy-TiO2 and rGO. In addition, it is also responsible for the partial transfer of electrons from rGO to VxOy-TiO2, which increases the synergistic interaction of the VxOy-TiO2-rGO hybrid to the reversible storage of lithium. In addition a full cell was created LiFePO4/VxOy-TiO2-rGO. The cell showed good cyclability while providing a capacity of 120 mAh g−1. Full article
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Open AccessCorrection
Correction: G. Papari et al. Terahertz Spectroscopy of Amorphous WSe2 and MoSe2 Thin Films. Materials 2018, 11, 1613
Materials 2020, 13(4), 1017; https://doi.org/10.3390/ma13041017 - 24 Feb 2020
Viewed by 609
Abstract
The exponential factor in Equation (1) of the paper published in Materials [1] reports a misprint and the correct expression of the transmission function is (1) T ˜ ( ω ) = E ˜ f ( ω ) E ˜ s ( ω ) = 2 n ˜ f ( n ˜ a + n ˜ s ) ( n ˜ f + n ˜ a ) ( n ˜ f + n ˜ s ) e x p {   i   ( n ˜ f n ˜ a ) ω t c } F P ( ω ) where F P ( ω ) = 1 1 ( n ˜ f n ˜ a n ˜ f + n ˜ a ) ( n ˜ f n ˜ s n ˜ f + n ˜ s ) e x p { i   2   n ˜ f ω t c } [...] Full article
(This article belongs to the Section Thin Films and Interfaces)
Open AccessArticle
Willow Bark for Sustainable Energy Storage Systems
Materials 2020, 13(4), 1016; https://doi.org/10.3390/ma13041016 - 24 Feb 2020
Cited by 2 | Viewed by 823
Abstract
Willow bark is a byproduct from forestry and is obtained at an industrial scale. We upcycled this byproduct in a two-step procedure into sustainable electrode materials for symmetrical supercapacitors using organic electrolytes. The procedure employed precarbonization followed by carbonization using different types of [...] Read more.
Willow bark is a byproduct from forestry and is obtained at an industrial scale. We upcycled this byproduct in a two-step procedure into sustainable electrode materials for symmetrical supercapacitors using organic electrolytes. The procedure employed precarbonization followed by carbonization using different types of KOH activation protocols. The obtained electrode materials had a hierarchically organized pore structure and featured a high specific surface area (>2500 m2 g−1) and pore volume (up to 1.48 cm3 g−1). The assembled supercapacitors exhibited capacitances up to 147 F g−1 in organic electrolytes concomitant with excellent cycling performance over 10,000 cycles at 0.6 A g−1 using coin cells. The best materials exhibited a capacity retention of 75% when changing scan rates from 2 to 100 mV s−1. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle
Strength Development and Elemental Distribution of Dolomite/Fly Ash Geopolymer Composite under Elevated Temperature
Materials 2020, 13(4), 1015; https://doi.org/10.3390/ma13041015 - 24 Feb 2020
Cited by 5 | Viewed by 1157
Abstract
A geopolymer has been reckoned as a rising technology with huge potential for application across the globe. Dolomite refers to a material that can be used raw in producing geopolymers. Nevertheless, dolomite has slow strength development due to its low reactivity as a [...] Read more.
A geopolymer has been reckoned as a rising technology with huge potential for application across the globe. Dolomite refers to a material that can be used raw in producing geopolymers. Nevertheless, dolomite has slow strength development due to its low reactivity as a geopolymer. In this study, dolomite/fly ash (DFA) geopolymer composites were produced with dolomite, fly ash, sodium hydroxide, and liquid sodium silicate. A compression test was carried out on DFA geopolymers to determine the strength of the composite, while a synchrotron Micro-Xray Fluorescence (Micro-XRF) test was performed to assess the elemental distribution in the geopolymer composite. The temperature applied in this study generated promising properties of DFA geopolymers, especially in strength, which displayed increments up to 74.48 MPa as the optimum value. Heat seemed to enhance the strength development of DFA geopolymer composites. The elemental distribution analysis revealed exceptional outcomes for the composites, particularly exposure up to 400 °C, which signified the homogeneity of the DFA composites. Temperatures exceeding 400 °C accelerated the strength development, thus increasing the strength of the DFA composites. This appears to be unique because the strength of ordinary Portland Cement (OPC) and other geopolymers composed of other raw materials is typically either maintained or decreases due to increased heat. Full article
(This article belongs to the Special Issue Obtaining and Characterization of New Materials)
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Open AccessArticle
Effects of Helix Geometry on Magnetic Guiding of Helical Polymer Composites on a Gastric Cancer Model: A Feasibility Study
Materials 2020, 13(4), 1014; https://doi.org/10.3390/ma13041014 - 24 Feb 2020
Cited by 1 | Viewed by 766
Abstract
This study investigates the effects of soft-robot geometry on magnetic guiding to develop an efficient helical mediator on a three-dimensional (3D) gastric cancer model. Four different magnetically active helical soft robots are synthesized by the inclusion of 5-μm iron particles in polydimethylsiloxane matrices. [...] Read more.
This study investigates the effects of soft-robot geometry on magnetic guiding to develop an efficient helical mediator on a three-dimensional (3D) gastric cancer model. Four different magnetically active helical soft robots are synthesized by the inclusion of 5-μm iron particles in polydimethylsiloxane matrices. The soft robots are named based on the diameter and length (D2-L15, D5-L20, D5-L25, and D5-L35) with samples having varied helical pitch and weight values. Then, the four samples are tested on a flat surface as well as a stomach model with various 3D wrinkles. We analyze the underlying physics of intermittent magnetomotility for the helix on a flat surface. In addition, we extract representative failure cases of magnetomotility on the stomach model. The D5-L25 sample was the most suitable among the four samples for a helical soft robot that can be moved to a target lesion by the magnetic-flux density of the stomach model. The effects of diameter, length, pitch, and weight of a helical soft robot on magnetomotility are discussed in order for the robot to reach the target lesion successfully via magnetomotility. Full article
(This article belongs to the Special Issue Programmable Anisotropic Materials and Composites)
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Open AccessCommunication
Monocytic Cell-Induced Phase Transformation of Circulating Lipid-Based Liquid Crystalline Nanosystems
Materials 2020, 13(4), 1013; https://doi.org/10.3390/ma13041013 - 24 Feb 2020
Cited by 2 | Viewed by 828
Abstract
Both lamellar and non-lamellar configurations are naturally present in bio-membranes, and the synthetic lipid-based liquid crystalline nano-assemblies, mimicking these unique structures, (including liposomes, cubosomes and hexosomes) are applicable in the controlled delivery of bioactives. However, it remains uncertain whether these nanosystems retain their [...] Read more.
Both lamellar and non-lamellar configurations are naturally present in bio-membranes, and the synthetic lipid-based liquid crystalline nano-assemblies, mimicking these unique structures, (including liposomes, cubosomes and hexosomes) are applicable in the controlled delivery of bioactives. However, it remains uncertain whether these nanosystems retain their original phase identity upon contact with blood circulating cells. This study highlights a novel biological cell flow-through approach at the synchrotron-based small angle X-ray scattering facility (bio-SAXS) to unravel their real-time phase evolution when incubated with human monocytic cells (THP-1) in suspension. Phytantriol-based cubosomes were identified to undergo monocytic cell-induced phase transformation from cubic to hexagonal phase periodicity. On the contrary, hexosomes exhibited time-dependent growth of a swollen hexagonal phase (i.e., larger lattice parameters) without displaying alternative phase characteristics. Similarly, liposomes remained undetectable for any newly evolved phase identity. Consequently, this novel in situ bio-SAXS study concept is valuable in delivering new important insights into the bio-fates of various lipid-based nanosystems under simulated human systemic conditions. Full article
(This article belongs to the Special Issue Advances in Bio-Inspired Materials for Medical Applications)
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Open AccessArticle
Topography of the Interfacial Shear Strength and the Mean Intrinsic Tensile Strength of Hemp Fibers as a Reinforcement of Polypropylene
Materials 2020, 13(4), 1012; https://doi.org/10.3390/ma13041012 - 24 Feb 2020
Viewed by 641
Abstract
The strength of the interphase between the reinforcements and the matrix has a major role in the mechanical properties of natural fiber reinforced polyolefin composites. The creation of strong interphases is hindered by the hydrophobic and hydrophilic natures of the matrix and the [...] Read more.
The strength of the interphase between the reinforcements and the matrix has a major role in the mechanical properties of natural fiber reinforced polyolefin composites. The creation of strong interphases is hindered by the hydrophobic and hydrophilic natures of the matrix and the reinforcements, respectively. Adding coupling agents has been a common strategy to solve this problem. Nonetheless, a correct dosage of such coupling agents is important to, on the one hand guarantee strong interphases and high tensile strengths, and on the other hand ensure a full exploitation of the strengthening capabilities of the reinforcements. The paper proposes using topographic profile techniques to represent the effect of reinforcement and coupling agent contents of the strength of the interphase and the exploitation of the reinforcements. This representation allowed identifying the areas that are more or less sensitive to coupling agent content. The research also helped by finding that an excess of coupling agent had less impact than a lack of this component. Full article
(This article belongs to the Special Issue Advances in Natural Fibers and Polymers)
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Open AccessArticle
The Heat Conductivity Properties of Hemp–Lime Composite Material Used in Single-Family Buildings
Materials 2020, 13(4), 1011; https://doi.org/10.3390/ma13041011 - 24 Feb 2020
Cited by 7 | Viewed by 1153
Abstract
The main goal of the paper is to calculate the heat conductivity for three experimental hemp–lime composites used for structural construction purposes with the use of the experimental stand inside two compartments. Due to current construction trends, we are constantly searching for eco-friendly [...] Read more.
The main goal of the paper is to calculate the heat conductivity for three experimental hemp–lime composites used for structural construction purposes with the use of the experimental stand inside two compartments. Due to current construction trends, we are constantly searching for eco-friendly materials that have a low carbon footprint. This is the case of the analyzed material, and additional thermographic heat distribution inside the material during a fire resistance test proves that it is also a perfect insulation material, which could be applied in addition of popular isolating materials. This paper presents the results of certain hemp–lime composite studies and the potential for using hemp–lime composite for the structural construction industry. Hemp–lime composite heat transfer coefficient, fire resistance, and bulk density properties are compared to those of other commonly used construction materials. The obtained results show that the material together with supporting beams made of other biodegradable materials can be the perfect alternative for other commonly used construction materials. Full article
(This article belongs to the Special Issue Energy in Construction and Building Materials)
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Open AccessArticle
Free Vibration Analysis of Curved Laminated Composite Beams with Different Shapes, Lamination Schemes, and Boundary Conditions
Materials 2020, 13(4), 1010; https://doi.org/10.3390/ma13041010 - 24 Feb 2020
Cited by 2 | Viewed by 631
Abstract
A general formulation is considered for the free vibration of curved laminated composite beams (CLCBs) with alterable curvatures and diverse boundary restraints. In accordance with higher-order shear deformation theory (HSDT), an improved variational approach is introduced for the numerical modeling. Besides, the multi-segment [...] Read more.
A general formulation is considered for the free vibration of curved laminated composite beams (CLCBs) with alterable curvatures and diverse boundary restraints. In accordance with higher-order shear deformation theory (HSDT), an improved variational approach is introduced for the numerical modeling. Besides, the multi-segment partitioning strategy is exploited for the derivation of motion equations, where the CLCBs are separated into several segments. Penalty parameters are considered to handle the arbitrary boundary conditions. The admissible functions of each separated beam segment are expanded in terms of Jacobi polynomials. The solutions are achieved through the variational approach. The proposed methodology can deal with arbitrary boundary restraints in a unified way by conveniently changing correlated parameters without interfering with the solution procedure. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessCommunication
The Preparation and Properties of a Shell Structure Ceramsite
Materials 2020, 13(4), 1009; https://doi.org/10.3390/ma13041009 - 24 Feb 2020
Viewed by 729
Abstract
In this paper, a shell structure ceramsite has been prepared and researched in order to attempt a new method of producing lightweight ceramsite. In the experiment, raw material was made into slurry and polypropylene balls were treated with the soak-and-pick process in the [...] Read more.
In this paper, a shell structure ceramsite has been prepared and researched in order to attempt a new method of producing lightweight ceramsite. In the experiment, raw material was made into slurry and polypropylene balls were treated with the soak-and-pick process in the slurry to make the green body; later, the green body was dried and fired in the furnace to make the shell structure ceramsite. The result showed that the shell structure ceramsite has an appropriate cylindrical compressive strength (0.87 MPa) with a bulk density at a low level (0.375 × 103 kg/m3), which can be used for lightweight concrete preparation, and with its special structure, it can be used for many other purposes. Full article
(This article belongs to the Section Construction and Building Materials)
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Open AccessArticle
An Enhanced Three-Dimensional Auxetic Lattice Structure with Improved Property
Materials 2020, 13(4), 1008; https://doi.org/10.3390/ma13041008 - 24 Feb 2020
Cited by 7 | Viewed by 864
Abstract
In order to enhance the mechanical property of auxetic lattice structures, a new enhanced auxetic lattice structure was designed by embedding narrow struts into a three-dimensional (3D) re-entrant lattice structure. A series of enhanced lattice structures with varied parameters were fabricated by 3D [...] Read more.
In order to enhance the mechanical property of auxetic lattice structures, a new enhanced auxetic lattice structure was designed by embedding narrow struts into a three-dimensional (3D) re-entrant lattice structure. A series of enhanced lattice structures with varied parameters were fabricated by 3D printing combined with the molten metal infiltration technique. Based on the method, parameter studies were performed. The enhanced auxetic lattice structure was found to exhibit superior mechanical behaviors compared to the 3D re-entrant lattice structure. An interesting phenomenon showed that increasing the diameter of connecting struts led to less auxetic and non-auxetic structures. Moreover, the compressive property of the enhanced structure also exhibited obvious dependence on the base material and compression directions. The present study can provide useful information for the design, fabrication and application of new auxetic structures with enhanced properties. Full article
(This article belongs to the Section Porous Materials)
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Open AccessArticle
Three-Dimensional Evaluation of Maxillary Sinus Changes in Growing Subjects: A Retrospective Cross-Sectional Study
Materials 2020, 13(4), 1007; https://doi.org/10.3390/ma13041007 - 24 Feb 2020
Cited by 16 | Viewed by 919
Abstract
This study aims to evaluate changes of maxillary sinuses in growing subjects. Cone Beam Computed Tomography (CBCT) scans of 146 patients were divided according to gender and age (6–8, 9–11, 12–14 years old). Left, right and total maxillary sinus volume (MSV-R, MSV-L, MSV-Tot) [...] Read more.
This study aims to evaluate changes of maxillary sinuses in growing subjects. Cone Beam Computed Tomography (CBCT) scans of 146 patients were divided according to gender and age (6–8, 9–11, 12–14 years old). Left, right and total maxillary sinus volume (MSV-R, MSV-L, MSV-Tot) and surface (MSS-R, MSS-L, MSS-Tot), left and right linear maximum width (LMW-L, LMW-R), depth (LMD-R, LMD-L) and height (LMH-R, LMH-R) were calculated using Mimics Research 22. Kruskal–Wallis Test and showed a statistically significant increase in both genders for all variables. Pairwise comparisons in females are always statistically significant in: LMH-R, LMH-R, MSS-Tot, MSV-Tot. All other variables showed a statistical significant increase between 9–11 and 12–14, and between 6–8 and 12–14 age groups, apart from LMSW-R, LMSW-L, LMSD-R, LMSD-L between 6–8 and 12–14 age groups. Pairwise comparisons in males are always and only statistically significant between 9–11 and 12–14, and between 6–8 and 12–14 groups. Symmetrical measurements (right and left) evaluated using Wilcoxon test retrieved no statistical significant difference. Comparisons between measurements on male and female subjects using Mann–Whitney test showed a statistical significant difference in 6–8 years group in MSV-R, MSV-L and MSV-Tot, and in 12–14 age group in MSV-R, MSV-L, MSV-Tot, MSS-r, MSS-l, MSS-Tot, MSW-R, MSW-L, MSD-R, MSD-L. Intraclass Correlation Coefficient (ICC) assessing inter-operator and intra-operator concordance retrieved excellent results for all variables. It appears that maxillary sinus growth resembles the differential peak of growth in male and female subjects. Sinuses starts to develop early in female subjects. However, in the first and last age group female sinuses are statistically significantly smaller compared to male ones. In male subjects, sinus growth occurs mainly between the second and third age group whilst in female subjects it starts between the first and second age group and continues between the second and the last. Sinus has a vertical development during the peak of growth, which is the main reason for its increase in volume. Full article
(This article belongs to the Special Issue Biomaterials and Technologies in Dentistry)
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Open AccessArticle
Nanoscale Plasticity Behavior of Additive-Manufactured Zirconia-Toughened Alumina Ceramics during Nanoindentation
Materials 2020, 13(4), 1006; https://doi.org/10.3390/ma13041006 - 24 Feb 2020
Cited by 2 | Viewed by 743
Abstract
The nanoscale plasticity phenomena in zirconia-toughened alumina (ZTA) ceramics with yttria-stabilized zirconia (YSZ) addition of 10% and 30% fabricated by additive manufacturing based on a stereolithography technique were explored in detail by nanoindentation and scanning electron microscopy. It was demonstrated that the initiation [...] Read more.
The nanoscale plasticity phenomena in zirconia-toughened alumina (ZTA) ceramics with yttria-stabilized zirconia (YSZ) addition of 10% and 30% fabricated by additive manufacturing based on a stereolithography technique were explored in detail by nanoindentation and scanning electron microscopy. It was demonstrated that the initiation of nanoscale plasticity was attributed to the combined contributions from the generation of nanoscale shear deformation bands and localized microcracking at the indentations. Such localized plastic behavior underneath the nanoindenter was interpreted by maximum shear stress analysis. The response of the phase boundary during indentation was emphasized through crack propagation paths, and optimization of alumina–YSZ adaptation through component design and SL processing was expected. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle
Orientation and Microstructure Evolution of Al-Al2Cu Regular Eutectic Lamellar Bifurcating in an Abruptly Changing Velocity under Directional Solidification
Materials 2020, 13(4), 1004; https://doi.org/10.3390/ma13041004 - 24 Feb 2020
Viewed by 593
Abstract
In an abruptly changing velocity under directional solidification, microstructures and the growth orientation of Al-Al2Cu eutectic lamellar were characterized. The change in solidification rate led to an interfacial instability, which results in a bifurcation of the eutectic lamella into new, refined [...] Read more.
In an abruptly changing velocity under directional solidification, microstructures and the growth orientation of Al-Al2Cu eutectic lamellar were characterized. The change in solidification rate led to an interfacial instability, which results in a bifurcation of the eutectic lamella into new, refined lamellae. The growth orientation of the eutectic Al2Cu phase was also only in its (001) direction and more strongly oriented to the heat flow direction. The results suggest that the eutectic lamellar Al-Al2Cu bifurcation and the spacing adjustment may be caused by the rate determining lateral diffusion of the solutes after interfacial instability. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessFeature PaperReview
Surface Modifications of Poly(Ether Ether Ketone) via Polymerization Methods—Current Status and Future Prospects
Materials 2020, 13(4), 999; https://doi.org/10.3390/ma13040999 - 23 Feb 2020
Cited by 6 | Viewed by 1204
Abstract
Surface modification of poly(ether ether ketone) (PEEK) aimed at applying it as a bone implant material aroused the unflagging interest of the research community. In view of the development of implantology and the growing demand for new biomaterials, increasing biocompatibility and improving osseointegration [...] Read more.
Surface modification of poly(ether ether ketone) (PEEK) aimed at applying it as a bone implant material aroused the unflagging interest of the research community. In view of the development of implantology and the growing demand for new biomaterials, increasing biocompatibility and improving osseointegration are becoming the primary goals of PEEK surface modifications. The main aim of this review is to summarize the use of polymerization methods and various monomers applied for surface modification of PEEK to increase its bioactivity, which is a critical factor for successful applications of biomedical materials. In addition, the future directions of PEEK surface modifications are suggested, pointing to low-ppm surface-initiated atom transfer radical polymerization (SI-ATRP) as a method with unexplored capacity for flat surface modifications. Full article
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Open AccessArticle
Chitosan-Functionalized Graphene Nanocomposite Films: Interfacial Interplay and Biological Activity
Materials 2020, 13(4), 998; https://doi.org/10.3390/ma13040998 - 23 Feb 2020
Cited by 6 | Viewed by 973
Abstract
Graphene oxide (GO) has recently captured tremendous attention, but only few functionalized graphene derivatives were used as fillers, and insightful studies dealing with the thermal, mechanical, and biological effects of graphene surface functionalization are currently missing in the literature. Herein, reduced [...] Read more.
Graphene oxide (GO) has recently captured tremendous attention, but only few functionalized graphene derivatives were used as fillers, and insightful studies dealing with the thermal, mechanical, and biological effects of graphene surface functionalization are currently missing in the literature. Herein, reduced graphene oxide (rGO), phosphorylated graphene oxide (PGO), and trimethylsilylated graphene oxide (SiMe3GO) were prepared by the post-modification of GO. The electrostatic interactions of these fillers with chitosan afforded colloidal solutions that provide, after water evaporation, transparent and flexible chitosan-modified graphene films. All reinforced chitosan–graphene films displayed improved mechanical, thermal, and antibacterial (S. aureus, E. coli) properties compared to native chitosan films. Hemolysis, intracellular catalase activity, and hemoglobin oxidation were also observed for these materials. This study shows that graphene functionalization provides a handle for tuning the properties of graphene-reinforced nanocomposite films and customizing their functionalities. Full article
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Open AccessArticle
First Large Scale Application with Self-Healing Concrete in Belgium: Analysis of the Laboratory Control Tests
Materials 2020, 13(4), 997; https://doi.org/10.3390/ma13040997 - 23 Feb 2020
Cited by 7 | Viewed by 1150
Abstract
Due to the negative impact of construction processes on the environment and a decrease in investments, there is a need for concrete structures to operate longer while maintaining their high performance. Self-healing concrete has the ability to heal itself when it is cracked, [...] Read more.
Due to the negative impact of construction processes on the environment and a decrease in investments, there is a need for concrete structures to operate longer while maintaining their high performance. Self-healing concrete has the ability to heal itself when it is cracked, thereby protecting the interior matrix as well as the reinforcement steel, resulting in an increased service life. Most research has focused on mortar specimens at lab-scale. Yet, to demonstrate the feasibility of applying self-healing concrete in practice, demonstrators of large-scale applications are necessary. A roof slab of an inspection pit was cast with bacterial self-healing concrete and is now in normal operation. As a bacterial additive to the concrete, a mixture called MUC+, made out of a Mixed Ureolytic Culture together with anaerobic granular bacteria, was added to the concrete during mixing. This article reports on the tests carried out on laboratory control specimens made from the same concrete batch, as well as the findings of an inspection of the roof slab under operating conditions. Lab tests showed that cracks at the bottom of specimens and subjected to wet/dry cycles had the best visual crack closure. Additionally, the sealing efficiency of cracked specimens submersed for 27 weeks in water, measured by means of a water permeability setup, was at least equal to 90%, with an efficiency of at least 98.5% for the largest part of the specimens. An inspection of the roof slab showed no signs of cracking, yet favorable conditions for healing were observed. So, despite the high healing potential that was recorded during lab experiments, an assessment under real-life conditions was not yet possible. Full article
(This article belongs to the Special Issue Self-Healing and Smart Cementitious Construction Materials)
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Open AccessArticle
Separation and Recovery of Refined Si from Al–Si Melt by Modified Czochralski Method
Materials 2020, 13(4), 996; https://doi.org/10.3390/ma13040996 - 23 Feb 2020
Viewed by 678
Abstract
Separation of refined silicon from Al–Si melt is still a puzzle for the solvent refining process, resulting in considerable waste of acid and silicon powder. A novel modified Czochralski method within the Al–Si alloy is proposed. After the modified Czochralski process, a large [...] Read more.
Separation of refined silicon from Al–Si melt is still a puzzle for the solvent refining process, resulting in considerable waste of acid and silicon powder. A novel modified Czochralski method within the Al–Si alloy is proposed. After the modified Czochralski process, a large amount of refined Si particles was enriched around the seed crystalline Si and separated from the Al–Si melt. As for the Al–28%Si with the pulling rate of 0.001 mm/min, the recovery of refined Si in the pulled-up alloy (PUA) sample is 21.5%, an improvement of 22% compared with the theoretical value, which is much larger 1.99 times than that in the remained alloy (RA) sample. The content of impurities in the PUA is much less than that in the RA sample, which indicates that the modified Czochralski method is effective to improve the removal fraction of impurities. The apparent segregation coefficients of boron (B) and phosphorus (P) in the PUA and RA samples were evaluated. These results demonstrate that the modified Czochralski method for the alloy system is an effective way to enrich and separate refined silicon from the Al–Si melt, which provide a potential and clean production of solar grade silicon (SoG-Si) for the future industrial application. Full article
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Open AccessArticle
Processing and Mechanical Properties of Ti2AlC MAX Phase Reinforced AE44 Magnesium Composite
Materials 2020, 13(4), 995; https://doi.org/10.3390/ma13040995 - 23 Feb 2020
Viewed by 997
Abstract
AE44 alloys and nanolaminated Ti2AlC particle-reinforced AE44 magnesium composites were synthesized by stir casting techniques and textured by hot extrusion methods. It was found that lamellar Al11RE3 precipitates spheroidized with the introduction of Ti2AlC into the [...] Read more.
AE44 alloys and nanolaminated Ti2AlC particle-reinforced AE44 magnesium composites were synthesized by stir casting techniques and textured by hot extrusion methods. It was found that lamellar Al11RE3 precipitates spheroidized with the introduction of Ti2AlC into the AE44 matrix. Both transmission electron microscope and planar disregistries calculations reveal a good match for interfacial lattice transition between Mg (0001) and the basal plane (0001) of Ti2AlC. This suggests that Ti2AlC is an efficient potent nucleating substrate for Mg, thus fertilizing the formation of strong interfacial bonds. After hot extrusion treatment, Ti2AlC particles were reoriented in the textured magnesium matrix, as confirmed by X-ray diffraction. This texture effect on the composite’s mechanical properties was carefully studied by tensile and compressive tests. Full article
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Open AccessArticle
Influence of Electroplated CBN Wheel Wear on Grinding Surface Morphology of Powder Metallurgy Superalloy FGH96
Materials 2020, 13(4), 1005; https://doi.org/10.3390/ma13041005 - 23 Feb 2020
Cited by 1 | Viewed by 763
Abstract
The electroplated cubic boron nitride (CBN) wheel has perfect precision retention and high-temperature grinding performance, which is widely used in the field of grinding difficult-to-cut materials, such as nickel-based superalloy. However, the research on the influence law and mechanism of grinding surface morphology [...] Read more.
The electroplated cubic boron nitride (CBN) wheel has perfect precision retention and high-temperature grinding performance, which is widely used in the field of grinding difficult-to-cut materials, such as nickel-based superalloy. However, the research on the influence law and mechanism of grinding surface morphology affected by the wear state of small-size grinding wheel is insufficient, which limits the further promotion and application of electroplated CBN wheel in the field of precision grinding of superalloy materials. Based on the in-depth analysis of the structure of FGH96 turbine disk, and combined with the actual processing requirements, the electroplated CBN wheel was designed, and the abrasive grains size selection experiments and CBN wheel wear experiments were then carried out for the powder metallurgy superalloy FGH96 in turn. The influence law of the abrasive grain size of CBN grinding wheel and the wear state of grinding wheel on the surface morphology was investigated, respectively. The obtained results showed that under the given processing parameters, the surface roughness Ra using 400# and 600# electroplated CBN wheels are around 0.66 μm and 0.53 μm during the normal wear state of grinding wheels, respectively, which can meet the requirement of surface quality less than Ra 0.8 μm in engineering application of turbine disk, and prove the feasibility of small-size CBN wheel grinding FGH96. In addition, the failure form of electroplated CBN wheel is mainly the accumulation and adhesion of abrasive debris, and the crushing and shedding of abrasive grain are hard to appear. Full article
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Open AccessArticle
Diamond Like Carbon Films Containing Si: Structure and Nonlinear Optical Properties
Materials 2020, 13(4), 1003; https://doi.org/10.3390/ma13041003 - 23 Feb 2020
Cited by 6 | Viewed by 800
Abstract
In the present research diamond-like carbon (DLC) films containing 4–29 at.% of silicon were deposited by reactive magnetron sputtering of carbon target. Study by X-ray photoelectron spectroscopy revealed the presence of Si–C bonds in the films. Nevertheless, a significant amount of Si–O–C and [...] Read more.
In the present research diamond-like carbon (DLC) films containing 4–29 at.% of silicon were deposited by reactive magnetron sputtering of carbon target. Study by X-ray photoelectron spectroscopy revealed the presence of Si–C bonds in the films. Nevertheless, a significant amount of Si–O–C and Si–Ox bonds was present too. The shape of the Raman scattering spectra of all studied diamond-like carbon containing silicon (DLC:Si) films was typical for diamond-like carbon. However, some peculiarities related to silicon doping were found. Studies on the dependence of DLC:Si of the optical transmittance spectra on the Si atomic concentration have shown that doping by silicon affects linear, as well as nonlinear, optical properties of the films. It is shown that the normalized reflectance of DLC:Si films decreased with the increased exciting light fluence. No clear relation between the normalized reflectance and photoexcited charge carrier relaxation time was found. It was suggested that that the normalized reflectance decrease with fluence can be related to nonlinear optical properties of the hydrogenated diamond-like carbon phase in DLC:Si film. Full article
(This article belongs to the Special Issue Advances in Diamond-Like Carbon (DLC) Films)
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Open AccessArticle
Towards the Use of Waste Pig Fat as a Novel Potential Bio-Based Rejuvenator for Recycled Asphalt Pavement
Materials 2020, 13(4), 1002; https://doi.org/10.3390/ma13041002 - 23 Feb 2020
Cited by 3 | Viewed by 944
Abstract
This article presents a novel potential bio-based rejuvenator derived from waste pig fat (WPF) for use in recycled asphalt applications. To achieve this purpose, the impact of different doses waste pig fat (e.g., 0, 3, 6, and 9 wt.% WPF) on the reclaimed [...] Read more.
This article presents a novel potential bio-based rejuvenator derived from waste pig fat (WPF) for use in recycled asphalt applications. To achieve this purpose, the impact of different doses waste pig fat (e.g., 0, 3, 6, and 9 wt.% WPF) on the reclaimed asphalt pavement binder (RAP-B) performance is investigated. The unmodified and WPF-modified asphalts are characterized by means of Fourier-transform infrared spectroscopy (FT-IR), thin-layer chromatography–flame ionization detection (TLC-FID), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Physico-rheological properties of asphalt blends are assessed through Brookfield viscometer, softening point, penetration, and dynamic shear rheometer (DSR) tests. TLC-FID data highlighted that incremental WPF addition into RAP-B restored its original balance maltenes-to-asphaltenes ratio; finding which was supported by FT-IR analysis. SEM disclosed that WPF has a great compatibility with the aged asphalt. AFM observations showed that grease treatment induced a decline in surface roughness (i.e., bee structures) and a rise in friction force (i.e., para-phase dimension) of RAP binder. TGA/DSC studies revealed that the bio-modifier not only possesses an excellent thermal stability but also can substantially enhance the binder low-temperature performance. Empirical and DSR tests demonstrated that WPF improved the low-temperature performance grade of RAP-B, reduced its mixing and compaction temperatures, and noticeably boosted its fatigue cracking resistance. The rejuvenation of aged asphalt employing WPF is feasible and can be an ideal approach to recycle both of RAP and waste pig fats. Full article
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Open AccessArticle
Low Cycle Fatigue Life Evaluation of Notched Specimens Considering Strain Gradient
Materials 2020, 13(4), 1001; https://doi.org/10.3390/ma13041001 - 23 Feb 2020
Viewed by 714
Abstract
An improved model based on the Chaboche constitutive model is proposed for cyclic plastic behavior of metal and low cycle fatigue of notched specimens under cyclic loading, considering the effect of strain gradient on nonlinear kinematic hardening and hysteresis behavior. The new model [...] Read more.
An improved model based on the Chaboche constitutive model is proposed for cyclic plastic behavior of metal and low cycle fatigue of notched specimens under cyclic loading, considering the effect of strain gradient on nonlinear kinematic hardening and hysteresis behavior. The new model is imported into the user material subroutine (UMAT) of the finite element computing software ABAQUS, and the strain gradient parameters required for model calculation are obtained by calling the user element subroutine (UEL). The effectiveness of the new model is tested by the torsion test of thin copper wire. Furthermore, the calibration method of strain gradient influence parameters of constitutive model is discussed by taking the notch specimen of Q235 steel as an example. The hysteresis behavior, strain distribution and fatigue failure of notched specimens under cyclic loading were simulated and analyzed with the new model. The results prove the rationality of the new model. Full article
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Open AccessArticle
Thermoplastic Starch (TPS) Films Added with Mucilage from Opuntia Ficus Indica: Mechanical, Microstructural and Thermal Characterization
Materials 2020, 13(4), 1000; https://doi.org/10.3390/ma13041000 - 23 Feb 2020
Cited by 2 | Viewed by 1031
Abstract
Opuntia cladodes are a typical vegetable waste, from which mucilage in gel form can be extracted. This work proposes blending it with a self-produced thermoplastic starch (TPS), originating from potato starch with a high content in glycerol (ca. 30%). Three methods were compared [...] Read more.
Opuntia cladodes are a typical vegetable waste, from which mucilage in gel form can be extracted. This work proposes blending it with a self-produced thermoplastic starch (TPS), originating from potato starch with a high content in glycerol (ca. 30%). Three methods were compared for extraction, bare maceration (MA), mechanical blending (ME) and mechanical blending following maceration (MPM) to produce films with an approximate thickness of 150 μm. For the comparison, tensile testing, differential scanning calorimetry and scanning electron microscopy were used. The MPM process proved the most effective, not only for extraction yielding, but also to obtain a larger deformation of the samples with respect to the one allowed by the pure TPS films. A considerable plasticization effect was observed. Despite this, the mechanical performance is still not completely satisfactory, and the expected effect of the calcium and magnesium salts contained in the mucilage to improve the rigidity of the TPS film was not really revealed. Prospected improvements would concern the fabrication process and the investigation of other possible loading modes and sample geometries. Full article
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Open AccessArticle
On Prediction of a Novel Chiral Material Y2H3O(OH): A Hydroxyhydride Holding Hydridic and Protonic Hydrogens
Materials 2020, 13(4), 994; https://doi.org/10.3390/ma13040994 - 22 Feb 2020
Cited by 1 | Viewed by 1012
Abstract
Examination of possible pathways of how oxygen atoms can be added to a yttrium oxyhydride system allowed us to predict new derivatives such as hydroxyhydrides possessing the composition M2H3O(OH) (M = Y, Sc, La, and Gd) in which three [...] Read more.
Examination of possible pathways of how oxygen atoms can be added to a yttrium oxyhydride system allowed us to predict new derivatives such as hydroxyhydrides possessing the composition M2H3O(OH) (M = Y, Sc, La, and Gd) in which three different anions (H-, O2−, and OH-) share the common chemical space. The crystal data of the solid hydroxyhydrides obtained on the base of DFT modeling correspond to the tetragonal structure that is characterized by the chiral space group P 4 1 . The analysis of bonding situation in M2H3O(OH) showed that the microscopic mechanism governing chemical transformations is caused by the displacements of protons which are induced by interaction with oxygen atoms incorporated into the crystal lattice of the bulk oxyhydride. The oxygen-mediated transformation causes a change in the charge state of some adjacent hydridic sites, thus forming protonic sites associated with hydroxyl groups. The predicted materials demonstrate a specific charge ordering that is associated with the chiral structural organization of the metal cations and the anions because their lattice positions form helical curves spreading along the tetragonal axis. Moreover, the effect of spatial twisting of the H- and H+ sites provides additional linking via strong dihydrogen bonds. The structure–property relationships have been investigated in terms of structural, mechanical, electron, and optical features. It was shown that good polar properties of the materials make them possible prototypes for the design of nonlinear optical systems. Full article
(This article belongs to the Special Issue Chiral Materials)
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Open AccessArticle
High Temperature Sensing and Detection for Cementitious Materials Using Manganese Violet Pigment
Materials 2020, 13(4), 993; https://doi.org/10.3390/ma13040993 - 22 Feb 2020
Cited by 2 | Viewed by 778
Abstract
In recent years, advanced materials have attracted considerable interest in the field of temperature detection and sensing. This study examined the thermochromic properties of inorganic manganese violet (MV) with increasing temperature. According to the thermochromic test, the material was found to have reversible [...] Read more.
In recent years, advanced materials have attracted considerable interest in the field of temperature detection and sensing. This study examined the thermochromic properties of inorganic manganese violet (MV) with increasing temperature. According to the thermochromic test, the material was found to have reversible and irreversible color change properties. The MV pigment was then applied to cementitious material at ratios of 1%, 3%, and 5%. The mixed cement samples with MV pigment were heated in a furnace, and digital images were captured at each temperature interval to evaluate the changes in the color information on the surface of the specimen. The mixed samples exhibited an irreversible thermochromic change from dark violet to grayish green above 400 °C. At the critical temperature of 440 °C, the RGB values increased by approximately 22%–55%, 28%–68%, and 7%–25%, depending on the content of MV pigment. In Lab space, the L value increased by approximately 23%–60% at 440 °C. The a value completely changed from positive to negative, and the b value changed from negative to positive. All the values differed according to the content of MV pigment at room temperature but approached similar ranges at the critical temperature, irrespective of the amount of MV pigment. To assess the changes in their microstructure and composition, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed on the samples exposed to temperatures ranging from room temperature to 450 °C. Full article
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