Materials

6 pages, 1093 KiB

Open AccessArticle

P3HT Nanofibrils Thin-Film Transistors by Adsorbing Deposition in Suspension

by Shuichi Nagamatsu, Masataka Ishida, Shougo Miyajima and Shyam S. Pandey

Materials 2019, 12(21), 3643; https://doi.org/10.3390/ma12213643 - 05 Nov 2019

Cited by 3 | Viewed by 2984

A novel film preparation method utilizing polymer suspension, entitled adsorbing deposition in suspensions (ADS), has been proposed. The poly(3-hexylthiophene) (P3HT) toluene solution forms P3HT nanofibrils dispersed suspension by aging. P3HT nanofibrils are highly crystallized with sharp vibronic absorption spectra. By the ADS method, [...] Read more.

A novel film preparation method utilizing polymer suspension, entitled adsorbing deposition in suspensions (ADS), has been proposed. The poly(3-hexylthiophene) (P3HT) toluene solution forms P3HT nanofibrils dispersed suspension by aging. P3HT nanofibrils are highly crystallized with sharp vibronic absorption spectra. By the ADS method, only P3HT nanofibrils in suspension can be deposited on the substrate surface without any disordered fraction from the dissolved P3HT in suspension. Formed ADS film contains only the nanostructured conjugated polymer. Fabricated polymer thin-film transistor (TFT) utilizing ADS P3HT film shows good TFT performances with low off current, narrow subthreshold swing and large on/off current ratio. Full article

(This article belongs to the Special Issue Organic-Semiconductor Based Devices)

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22 pages, 8732 KiB

Open AccessFeature PaperArticle

Proposing a New Method Based on Image Analysis to Estimate the Segregation Index of Lightweight Aggregate Concretes

by Afonso Miguel Solak, Antonio José Tenza-Abril, Francisco Baeza-Brotons and David Benavente

Materials 2019, 12(21), 3642; https://doi.org/10.3390/ma12213642 - 05 Nov 2019

Cited by 13 | Viewed by 2945

Abstract

This work presents five different methods for quantifying the segregation phenomenon in lightweight aggregate concretes (LWAC). The use of LWACs allows greater design flexibility and substantial cost savings, and has a positive impact on the energy consumption of a building. However, these materials [...] Read more.

This work presents five different methods for quantifying the segregation phenomenon in lightweight aggregate concretes (LWAC). The use of LWACs allows greater design flexibility and substantial cost savings, and has a positive impact on the energy consumption of a building. However, these materials are susceptible to aggregate segregation, which causes an irregular distribution of the lightweight aggregates in the mixture and may affect the concrete properties. To quantify this critical process, a new method based on image analysis is proposed and its results are compared to the well-established methods of density and ultrasonic pulse velocity measurement. The results show that the ultrasonic test method presents a lower accuracy than the other studied methods, although it is a nondestructive test, easy to perform, and does not need material characterization. The new methodology via image analysis has a strong correlation with the other methods, it considers information from the complete section of the samples, and it does not need the horizontal cut of the specimens or material characterization. Full article

(This article belongs to the Special Issue Advances in Lightweight Aggregate Concrete)

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27 pages, 8555 KiB

Open AccessReview

Dielectric and Energy Storage Properties of Ba_(1−x)Ca_xZr_yTi_(1−y)O₃ (BCZT): A Review

by Mudassar Maraj, Wenwang Wei, Biaolin Peng and Wenhong Sun

Materials 2019, 12(21), 3641; https://doi.org/10.3390/ma12213641 - 05 Nov 2019

Cited by 56 | Viewed by 6929

Abstract

The Ba_(1−x)Ca_xZr_yTi_(1−y)O₃ (BCZT), a lead-free ceramic material, has attracted the scientific community since 2009 due to its large piezoelectric coefficient and resulting high dielectric permittivity. This perovskite material is a characteristic dielectric material for [...] Read more.

The Ba_(1−x)Ca_xZr_yTi_(1−y)O₃ (BCZT), a lead-free ceramic material, has attracted the scientific community since 2009 due to its large piezoelectric coefficient and resulting high dielectric permittivity. This perovskite material is a characteristic dielectric material for the pulsed power capacitors industry currently, which in turn leads to devices for effective storage and supply of electric energy. After this remarkable achievement in the area of lead-free piezoelectric ceramics, the researchers are exploring both the bulk as well as thin films of this perovskite material. It is observed that the thin film of this materials have outstandingly high power densities and high energy densities which is suitable for electrochemical supercapacitor applications. From a functional materials point of view this material has also gained attention in multiferroic composite material as the ferroelectric constituent of these composites and has provided extraordinary electric properties. This article presents a review on the relevant scientific advancements that have been made by using the BCZT materials for electric energy storage applications by optimizing its dielectric properties. The article starts with a BCZT introduction and discussion of the need of this material for high energy density capacitors, followed by different synthesis techniques and the effect on dielectric properties of doping different materials in BCZT. The advantages of thin film BCZT material over bulk counterparts are also discussed and its use as one of the constituents of mutiferroic composites is also presented. Finally, it summarizes the future prospects of this material followed by the conclusions. Full article

(This article belongs to the Special Issue Advances in Multiferroics)

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2 pages, 154 KiB

Open AccessReply

Author Response to Comment on: Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review

by Guijun Yang and Soo-Jin Park

Materials 2019, 12(21), 3640; https://doi.org/10.3390/ma12213640 - 05 Nov 2019

Cited by 35 | Viewed by 1939

Abstract

We recently published an article “Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review” on Materials, and we are honored to receive a comment article from Jalouli et al. We will give a detailed explanation for the confusion of the [...] Read more.

We recently published an article “Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review” on Materials, and we are honored to receive a comment article from Jalouli et al. We will give a detailed explanation for the confusion of the mechanism of crystal nucleation and growth in the comment article. Full article

(This article belongs to the Special Issue Conventional and Microwave Hydrothermal Synthesis of Functional Materials)

10 pages, 2155 KiB

Open AccessArticle

Highly Transparent and Surface-Plasmon-Enhanced Visible-Photodetector Based on Zinc Oxide Thin-Film Transistors with Heterojunction Structure

by Cheng-Jyun Wang, Hsin-Chiang You, Kuan Lin, Jen-Hung Ou, Keng-Hsien Chao and Fu-Hsiang Ko

Materials 2019, 12(21), 3639; https://doi.org/10.3390/ma12213639 - 05 Nov 2019

Cited by 5 | Viewed by 2719

Abstract

Highly transparent zinc oxide (ZnO)-based thin-film transistors (TFTs) with gold nanoparticles (AuNPs) capable of detecting visible light were fabricated through spray pyrolysis on a fluorine-doped tin oxide substrate. The spray-deposited channel layer of ZnO had a thickness of approximately 15 nm, and the [...] Read more.

Highly transparent zinc oxide (ZnO)-based thin-film transistors (TFTs) with gold nanoparticles (AuNPs) capable of detecting visible light were fabricated through spray pyrolysis on a fluorine-doped tin oxide substrate. The spray-deposited channel layer of ZnO had a thickness of approximately 15 nm, and the thickness exhibited a linear increase with an increasing number of sprays. Furthermore, the ZnO thin-film exhibited a markedly smoother channel layer with a significantly lower surface roughness of 1.84 nm when the substrate was 20 cm from the spray nozzle compared with when it was 10 cm away. Finally, a ZnO and Au-NP heterojunction nanohybrid structure using plasmonic energy detection as an electrical signal, constitutes an ideal combination for a visible-light photodetector. The ZnO-based TFTs convert localized surface plasmon energy into an electrical signal, thereby extending the wide band-gap of materials used for photodetectors to achieve visible-light wavelength detection. The photo-transistors demonstrate an elevated on-current with an increase of the AuNP density in the concentration of 1.26, 12.6, and 126 pM and reach values of 3.75, 5.18, and 9.79 × 10⁻⁷ A with applied gate and drain voltages. Moreover, the threshold voltage (Vth) also drifts to negative values as the AuNP density increases. Full article

(This article belongs to the Section Electronic Materials)

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11 pages, 5268 KiB

Open AccessArticle

Thermoresistive Properties of Graphite Platelet Films Supported by Different Substrates

by Mariano Palomba, Gianfranco Carotenuto, Angela Longo, Andrea Sorrentino, Antonio Di Bartolomeo, Laura Iemmo, Francesca Urban, Filippo Giubileo, Gianni Barucca, Massimo Rovere, Alberto Tagliaferro, Giuseppina Ambrosone and Ubaldo Coscia

Materials 2019, 12(21), 3638; https://doi.org/10.3390/ma12213638 - 05 Nov 2019

Cited by 6 | Viewed by 2427

Abstract

Large-area graphitic films, produced by an advantageous technique based on spraying a graphite lacquer on glass and low-density polyethylene (LDPE) substrates were studied for their thermoresistive applications. The spray technique uniformly covered the surface of the substrate by graphite platelet (GP) unities, which [...] Read more.

Large-area graphitic films, produced by an advantageous technique based on spraying a graphite lacquer on glass and low-density polyethylene (LDPE) substrates were studied for their thermoresistive applications. The spray technique uniformly covered the surface of the substrate by graphite platelet (GP) unities, which have a tendency to align parallel to the interfacial plane. Transmission electron microscopy analysis showed that the deposited films were composed of overlapped graphite platelets of different thickness, ranging from a few tens to hundreds of graphene layers, and Raman measurements provided evidence for a good graphitic quality of the material. The GP films deposited on glass and LDPE substrates exhibited different thermoresistive properties during cooling–heating cycles in the −40 to +40 °C range. Indeed, negative values of the temperature coefficient of resistance, ranging from −4 × 10⁻⁴ to −7 × 10⁻⁴ °C⁻¹ have been observed on glass substrates, while positive values varying between 4 × 10⁻³ and 8 × 10⁻³ °C⁻¹ were measured when the films were supported by LDPE. These behaviors were attributed to the different thermal expansion coefficients of the substrates. The appreciable thermoresistive properties of the graphite platelet films on LDPE could be useful for plastic electronic applications. Full article

(This article belongs to the Special Issue Carbon-Based Materials)

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11 pages, 3146 KiB

Open AccessArticle

VXC-72R/ZrO₂/GCE-Based Electrochemical Sensor for the High-Sensitivity Detection of Methyl Parathion

by Runqiang Liu, Yashuang Wang, Bo Li, Binbin Liu, Huina Ma, Dongdong Li, Li Dong, Fang Li, Xiling Chen and Xinming Yin

Materials 2019, 12(21), 3637; https://doi.org/10.3390/ma12213637 - 05 Nov 2019

Cited by 21 | Viewed by 2580

Abstract

In this work, a carbon black (VXC-72R)/zirconia (ZrO₂) nanocomposite-modified glassy carbon electrode (GCE) was designed, and a VXC-72R/ZrO₂/GCE-based electrochemical sensor was successfully fabricated for the high-sensitivity detection of methyl parathion (MP). Electrochemical measurements showed that the VXC-72R/ZrO₂/GCE-based [...] Read more.

In this work, a carbon black (VXC-72R)/zirconia (ZrO₂) nanocomposite-modified glassy carbon electrode (GCE) was designed, and a VXC-72R/ZrO₂/GCE-based electrochemical sensor was successfully fabricated for the high-sensitivity detection of methyl parathion (MP). Electrochemical measurements showed that the VXC-72R/ZrO₂/GCE-based electrochemical sensor could make full use of the respective advantages of the VXC-72R and ZrO₂ nanoparticles to enhance the MP determination performance. The VXC-72R nanoparticles had high electrical conductivity and a large surface area, and the ZrO₂ nanoparticles possessed a strong affinity to phosphorus groups, which could achieve good organophosphorus adsorption. On the basis of the synergistic effect generated from the interaction between the VXC-72R and ZrO₂ nanoparticles, the VXC-72R/ZrO₂/GCE-based electrochemical sensor could show excellent trace analysis determination performance. The low detection limit could reach up to 0.053 μM, and there was a linear concentration range of 1 μM to 100 μM. Such a high performance indicates that the VXC-72R/ZrO₂/GCE-based electrochemical sensor has potential in numerous foreground applications. Full article

(This article belongs to the Section Advanced Composites)

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15 pages, 7024 KiB

Open AccessArticle

Investigations on Aging Behavior and Mechanism of Polyurea Coating in Marine Atmosphere

by Kaiyuan Che, Ping Lyu, Fei Wan and Mingliang Ma

Materials 2019, 12(21), 3636; https://doi.org/10.3390/ma12213636 - 05 Nov 2019

Cited by 37 | Viewed by 4998

Abstract

In this investigation, the aging behaviors of polyurea coating exposed to marine atmosphere for 150 days were studied and the mechanism was analyzed. The influences on surface and mechanical properties, surface morphology, thermal stability behavior, as well as chemical changes evolution of the [...] Read more.

In this investigation, the aging behaviors of polyurea coating exposed to marine atmosphere for 150 days were studied and the mechanism was analyzed. The influences on surface and mechanical properties, surface morphology, thermal stability behavior, as well as chemical changes evolution of the coating were investigated. By attenuated total reflectance fourier transform infrared spectroscopy (ATR–FTIR) and X-ray photoelectron spectroscopy (XPS), changes in the chemical properties of polyurea coatings before (PCB) and after 150 d (PCA) of aging were analyzed, and emphasis was given to the effect of aging on functional group change, the hydrogen bonding behavior, and phase separated morphology. The results displayed prominent chain scission during aging, such as N–H, C=O, and C–O–C and the hydrogen bonded urea carbonyl content showed a decrease trend. The relative content of soft and hard segments showed a significant change, which increased the degree of phase separation. Full article

(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection)

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Graphical abstract

17 pages, 6928 KiB

Open AccessArticle

Effect of Centrifugal Shot Peening on the Surface Properties of Laser-Cut C45 Steel Parts

by Agnieszka Skoczylas and Kazimierz Zaleski

Materials 2019, 12(21), 3635; https://doi.org/10.3390/ma12213635 - 05 Nov 2019

Cited by 16 | Viewed by 2721

Abstract

This article presents the results of experimental studies of the impact of centrifugal shot peening parameters on the roughness, microstructure, and microhardness of the surface layer of laser-cut C45 steel parts. Residual stress distributions and the presence of iron oxides on the surface [...] Read more.

This article presents the results of experimental studies of the impact of centrifugal shot peening parameters on the roughness, microstructure, and microhardness of the surface layer of laser-cut C45 steel parts. Residual stress distributions and the presence of iron oxides on the surface of these elements were also examined. Centrifugal shot peening tests were performed on an FV-580a vertical machining center while using a specially designed peening head. The parameters that were varied during centrifugal shot peening included tangential speed of the tool v_g and feed rate v_f. The use of centrifugal shot peening for finish machining of laser-cut C45 steel parts allowed for obtaining a four-fold reduction in the surface roughness parameters Ra and Rz. As a result of shot peening, the geometrical structure of the surface of the steel parts was modified and it acquired new beneficial features, such as large values of the rounding radii of the micropeaks and high material ratios (Rmr_max = 92%). At the same time, the surface layer was hardened (microhardness increased by 16%) and a compressive residual stress layer was produced on the surface of the workpieces. Additionally, as the shot impacted the processed surface, combustion products were “blasted” or “sheared” off it. Shot peening using the proposed technique can be successfully performed while using CNC machines. Full article

(This article belongs to the Section Carbon Materials)

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17 pages, 1927 KiB

Open AccessArticle

Hybrid Systems Based on Talc and Chitosan for Controlled Drug Release

by Luciano C. B. Lima, Caio C. Coelho, Fabrícia C. Silva, Andréia B. Meneguin, Hernane S. Barud, Roosevelt D. S. Bezerra, Cesar Viseras, Josy A. Osajima and Edson C. Silva-Filho

Materials 2019, 12(21), 3634; https://doi.org/10.3390/ma12213634 - 05 Nov 2019

Cited by 15 | Viewed by 3059

Abstract

Inorganic matrices and biopolymers have been widely used in pharmaceutical fields. They show properties such as biocompatibility, incorporation capacity, and controlled drug release, which can become more attractive if they are combined to form hybrid materials. This work proposes the synthesis of new [...] Read more.

Inorganic matrices and biopolymers have been widely used in pharmaceutical fields. They show properties such as biocompatibility, incorporation capacity, and controlled drug release, which can become more attractive if they are combined to form hybrid materials. This work proposes the synthesis of new drug delivery systems (DDS) based on magnesium phyllosilicate (Talc) obtained by the sol–gel route method, the biopolymer chitosan (Ch), and the inorganic-organic hybrid formed between this matrix (Talc + Ch), obtained using glutaraldehyde as a crosslink agent, and to study their incorporation/release capacity of amiloride as a model drug. The systems were characterized by X-ray diffraction (XRD), Therma analysis TG/DTG, and Fourier-transform infrared spectroscopy (FTIR) that supported the DDS’s formation. The hybrid showed a better drug incorporation capacity compared to the precursors, with a loading of 55.74, 49.53, and 4.71 mg g⁻¹ for Talc + Ch, Talc, and Ch, respectively. The release assays were performed on a Hanson Research SR-8 Plus dissolver using apparatus I (basket), set to guarantee the sink conditions. The in vitro release tests showed a prolongation of the release rates of this drug for at least 4 h. This result proposes that the systems implies the slow and gradual release of the active substance, favoring the maintenance of the plasma concentration within a therapeutic window. Full article

(This article belongs to the Special Issue Advances in Polysaccharide Biomaterials)

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12 pages, 4666 KiB

Open AccessArticle

Human Mesenchymal Stem Cell Combined with a New Strontium-Enriched Bioactive Glass: An ex-vivo Model for Bone Regeneration

by Devis Bellucci, Elena Veronesi, Valentina Strusi, Tiziana Petrachi, Alba Murgia, Ilenia Mastrolia, Massimo Dominici and Valeria Cannillo

Materials 2019, 12(21), 3633; https://doi.org/10.3390/ma12213633 - 05 Nov 2019

Cited by 25 | Viewed by 2944

Abstract

A 3D cellular model that mimics the potential clinical application of a biomaterial is here applied for the first time to a bioactive glass, in order to assess its biological potential. A recently developed bioactive glass (BGMS10), whose composition contained strontium and magnesium, [...] Read more.

A 3D cellular model that mimics the potential clinical application of a biomaterial is here applied for the first time to a bioactive glass, in order to assess its biological potential. A recently developed bioactive glass (BGMS10), whose composition contained strontium and magnesium, was produced in the form of granules and fully investigated in terms of biocompatibility in vitro. Apart from standard biological characterization (Simulated Body Fluid (SBF) testing and biocompatibility as per ISO10993), human bone marrow mesenchymal stromal/stem cells (BM-MSCs) were used to investigate the performance of the bioactive glass granules in an innovative 3D cellular model. The results showed that BGMS10 supported human BM-MSCs adhesion, colonization, and bone differentiation. Thus, bioactive glass granules seem to drive osteogenic differentiation and thus look particularly promising for orthopedic applications, bone tissue engineering and regenerative medicine. Full article

(This article belongs to the Special Issue Spotlight on Bioactive Glasses and Their Related Composites)

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12 pages, 5203 KiB

Open AccessFeature PaperArticle

Effect of the Post-Spinning Solvent Exchange on the Performance of Asymmetric, Polyimide Hollow Fibers Prepared by Using a Triple-Orifice Spinneret

by Paola Bernardo, Franco Tasselli, Giovanni Chiappetta and Gabriele Clarizia

Materials 2019, 12(21), 3632; https://doi.org/10.3390/ma12213632 - 05 Nov 2019

Cited by 7 | Viewed by 2121

Abstract

Hollow fibers (HFs) are widely applied in different membrane operations, particularly in gas separation. The present work investigates the effect of post-spinning treatment on the gas transport properties of polyimide-based HFs. The membranes were spun by using both a conventional spinneret and a [...] Read more.

Hollow fibers (HFs) are widely applied in different membrane operations, particularly in gas separation. The present work investigates the effect of post-spinning treatment on the gas transport properties of polyimide-based HFs. The membranes were spun by using both a conventional spinneret and a triple-orifice spinneret. A systematic analysis was carried out by considering different alcohols as the first fluid for the solvent exchange, with or without n–hexane as a second fluid. The HFs were characterized by exploring the change of the morphology and the permselective properties as a consequence of the operation conditions for spinning and post-treatments. According to the morphology, for a specific hollow fiber type, an optimal post–treatment was identified. The HFs prepared with the triple-orifice spinneret, using a solvent–rich shell fluid, can take advantage of the post-treatment using larger alcohols, while smaller alcohols should be preferred for the conventional spun HFs that present inside–outside double skin layers. Full article

(This article belongs to the Special Issue Membrane Materials for Gas Separation)

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2 pages, 163 KiB

Open AccessComment

A comment on: “Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review”

by Behrouz Jalouli, Aref Abbasi and S. Mohammad Musavi Khoei

Materials 2019, 12(21), 3631; https://doi.org/10.3390/ma12213631 - 05 Nov 2019

Cited by 12 | Viewed by 2137

Abstract

In the recent paper published in Materials (Yang et al., 2019), there is a mistake in the explanation of crystal growth mechanism of the hydrothermal method. The error in this article is discussed in this short communication. Full article

(This article belongs to the Special Issue Conventional and Microwave Hydrothermal Synthesis of Functional Materials)

9 pages, 5011 KiB

Open AccessArticle

The Wear Responses of the Welded Joints of ASTM A335 Gr. P11 Steels Affected by Accelerated Flow Corrosion

by Javier Montero, Almudena Filgueira, Ana García-Diez, José Luís Mier and Carolina Camba

Materials 2019, 12(21), 3630; https://doi.org/10.3390/ma12213630 - 04 Nov 2019

Cited by 1 | Viewed by 2841

Abstract

This study shows the effects of wear on welded joints of ASTM A355 Gr. P11 “Seamless Ferritic Alloy-Steel Pipe for High Temperature Service” steels subjected to the welding procedures established by codes B31.1 and ASME III. The standard welding procedure establishes the following [...] Read more.

This study shows the effects of wear on welded joints of ASTM A355 Gr. P11 “Seamless Ferritic Alloy-Steel Pipe for High Temperature Service” steels subjected to the welding procedures established by codes B31.1 and ASME III. The standard welding procedure establishes the following steps: a preheating process, welding and post-weld heat treatment. This generates a wear behavior that depends on the thermal cycles to which the different areas of the joint are subjected. The objective of this article was the study of the behavior against the flow-accelerated corrosion of the welded joints of a low alloy steel. There is the possibility of establishing welding procedures other than those established, while maintaining the safety ranges, depending on the field of application for the steel. Full article

(This article belongs to the Special Issue Advanced Manufacturing of Metallic Alloys)

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14 pages, 2142 KiB

Open AccessArticle

Cost Analysis of Prefabricated Elements of the Ordinary and Lightweight Concrete Walls in Residential Construction

by Marzena Kurpinska, Beata Grzyl and Adam Kristowski

Materials 2019, 12(21), 3629; https://doi.org/10.3390/ma12213629 - 04 Nov 2019

Cited by 20 | Viewed by 4346

Abstract

Global economic growth causes an increase in natural resources exploitation, particularly in construction branch. The growing use of electricity contributes to climate change. Therefore, it is necessary to search the solutions, which will allow for reducing natural resources exploitation. One of the many [...] Read more.

Global economic growth causes an increase in natural resources exploitation, particularly in construction branch. The growing use of electricity contributes to climate change. Therefore, it is necessary to search the solutions, which will allow for reducing natural resources exploitation. One of the many opportunities to do that is the application of the recycled materials. The authors of the given article have analyzed three variants of construction solutions. One of them was the production of the walls of a building from reinforced concrete prefabricates with styrofoam insulation layer. The second variant for analysis were prefabricated walls from lightweight concrete, made of sintered clay aggregate with a foam core. The third proposed variant was a system of multi-layered walls, which was made of lightweight concrete with granulated expanded glass aggregate (GEGA). The main objective of the research was to assess the use of lightweight GEGA prefabricates, focusing on economic and technological aspects of the solution. The authors have analyzed the entire construction costs; ceilings and stairs were assumed as reinforced concrete elements. In calculations, the weight of the elements was taken into account, as well as transportation and mounting costs. On the basis of this cost analysis, it was concluded that the use of prefabricated element, made of lightweight concrete with GEGA, could be a replacement for the solutions, widely applied until these days. The analysis has also shown that the use of prefabricates with GEGA is sensible from the economic viewpoint, as it allows for saving construction time. Moreover, the solutions, proposed here, allow for saving natural resources and assuming a more environmentally friendly and caring attitude. Full article

(This article belongs to the Special Issue Mechanical, Thermal, and Hygric Properties of Lightweight Composites for Construction Use)

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13 pages, 6003 KiB

Open AccessArticle

Feasibility of ANFIS-PSO and ANFIS-GA Models in Predicting Thermophysical Properties of Al₂O₃-MWCNT/Oil Hybrid Nanofluid

by Ibrahim M. Alarifi, Hoang M. Nguyen, Ali Naderi Bakhtiyari and Amin Asadi

Materials 2019, 12(21), 3628; https://doi.org/10.3390/ma12213628 - 04 Nov 2019

Cited by 86 | Viewed by 5049

Abstract

The main purpose of the present paper is to improve the performance of the adaptive neuro-fuzzy inference system (ANFIS) in predicting the thermophysical properties of Al₂O₃-MWCNT/thermal oil hybrid nanofluid through mixing using metaheuristic optimization techniques. A literature survey showed [...] Read more.

The main purpose of the present paper is to improve the performance of the adaptive neuro-fuzzy inference system (ANFIS) in predicting the thermophysical properties of Al₂O₃-MWCNT/thermal oil hybrid nanofluid through mixing using metaheuristic optimization techniques. A literature survey showed that the use of an artificial neural network (ANN) is the most widely used method, although there are other methods that showed better performance. Moreover, it was found in the literature that artificial intelligence methods have been widely used for predicting the thermal conductivity of nanofluids. Thus, in the present study, genetic algorithms (GAs) and particle swarm optimization (PSO) have been utilized to search and determine the antecedent and consequent parameters of the ANFIS model. Solid concentration and temperature were considered as input variables, and thermal conductivity, dynamic viscosity, heat transfer performance, and pumping power in both the internal laminar and turbulent flow regimes were the outputs. In order to evaluate and compare the performance of the models, two statistical indices of root mean square error (RMSE) and determination coefficient (R) were utilized. Based on the results, both of the models are able to predict the thermophysical properties appropriately. However, the ANFIS-PSO model had a better performance than the ANFIS-GA model. Finally, the studied thermophysical properties were developed by the trained ANFIS-PSO model. Full article

(This article belongs to the Special Issue Nanofluids: From Fundamental Sciences to Applications)

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17 pages, 4248 KiB

Open AccessArticle

Mechanical Properties, Biodegradation, and Biocompatibility of Ultrafine Grained Magnesium Alloy WE43

by Sergey Dobatkin, Natalia Martynenko, Natalia Anisimova, Mikhail Kiselevskiy, Dmitriy Prosvirnin, Vladimir Terentiev, Nikita Yurchenko, Gennady Salishchev and Yuri Estrin

Materials 2019, 12(21), 3627; https://doi.org/10.3390/ma12213627 - 04 Nov 2019

Cited by 25 | Viewed by 3149

Abstract

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studied. The grain refinement down to 0.93 ± 0.29 µm and [...] Read more.

In this work, the effect of an ultrafine-grained (UFG) structure obtained by multiaxial deformation (MAD) on the mechanical properties, fatigue strength, biodegradation, and biocompatibility in vivo of the magnesium alloy WE43 was studied. The grain refinement down to 0.93 ± 0.29 µm and the formation of Mg₄₁Nd₅ phase particles with an average size of 0.34 ± 0.21 µm were shown to raise the ultimate tensile strength to 300 MPa. Besides, MAD improved the ductility of the alloy, boosting the total elongation from 9% to 17.2%. An additional positive effect of MAD was an increase in the fatigue strength of the alloy from 90 to 165 MPa. The formation of the UFG structure also reduced the biodegradation rate of the alloy under both in vitro and in vivo conditions. The relative mass loss after six weeks of experiment was 83% and 19% in vitro and 46% and 7% in vivo for the initial and the deformed alloy, respectively. Accumulation of hydrogen and the formation of necrotic masses were observed after implantation of alloy specimens in both conditions. Despite these detrimental phenomena, the desired replacement of the implant and the surrounding cavity with new connective tissue was observed in the areas of implantation. Full article

(This article belongs to the Special Issue Alloys for Biomedical Application)

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14 pages, 7274 KiB

Open AccessArticle

Superior Strength and Ductility of In Situ Nano TiB₂/Al–Cu–Mg Composites by Cold Rolling and Post-Aging Treatment

by Junhui Tang, Jiwei Geng, Cunjuan Xia, Mingliang Wang, Dong Chen and Haowei Wang

Materials 2019, 12(21), 3626; https://doi.org/10.3390/ma12213626 - 04 Nov 2019

Cited by 4 | Viewed by 2181

Abstract

In this work, the combination of cold rolling with post-aging treatment is developed to achieve the optimal strength–ductility for the in situ nano TiB₂/Al–Cu–Mg composite. The microstructure and mechanical properties of the composite subjected to 20% thickness reduction of cold rolling [...] Read more.

In this work, the combination of cold rolling with post-aging treatment is developed to achieve the optimal strength–ductility for the in situ nano TiB₂/Al–Cu–Mg composite. The microstructure and mechanical properties of the composite subjected to 20% thickness reduction of cold rolling at room temperature and their evolutions upon post-aging at different temperatures were investigated by means of a tensile test, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the TiB₂ particles were effective in dislocation pinning and accumulation during the cold-rolling process. The tensile tests indicated that both the yield and ultimate tensile strengths of the cold-rolling sample increased a lot due to the dislocation strengthening and precipitation strengthening generated by dynamic precipitation during cold rolling in comparison with the conventional T6 sample. After aging at 100 °C/12 h, the elongation to failure reached ~8.4%, which was higher than the conventional T6 sample. Meanwhile, there was also a dramatic increase of strength. The yield and ultimate tensile strengths are ~644 MPa and ~726 MPa, respectively. This remarkable strength–ductility combination was due to the modified microstructure caused prior to artificial aging by the cold-rolling method and the formation of nanosized Guinier–Preston–Bagaryatsky (GPB) zones. The underlying mechanisms related to the superior strength–ductility combination were discussed regarding the microstructural characteristics in the composite. Full article

(This article belongs to the Section Advanced Composites)

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15 pages, 10693 KiB

Open AccessArticle

Effect of Thermal Cycle on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Low-Alloy Steel

by Xueliang Kang, Shiyun Dong, Hongbin Wang, Shixing Yan, Xiaoting Liu and Huiping Ren

Materials 2019, 12(21), 3625; https://doi.org/10.3390/ma12213625 - 04 Nov 2019

Cited by 4 | Viewed by 2437

Abstract

Low-alloy steel samples were successfully fabricated by selective laser melting (SLM). The evolution of the microstructure and the mechanical properties were investigated with different values of the energy area density (EAD). The results revealed that the initial solidification microstructures of the single tracks [...] Read more.

Low-alloy steel samples were successfully fabricated by selective laser melting (SLM). The evolution of the microstructure and the mechanical properties were investigated with different values of the energy area density (EAD). The results revealed that the initial solidification microstructures of the single tracks with different EADs were all martensite. However, the microstructures of bulk samples under different EADs were not martensite and differed significantly even from one another. When EAD increased from 47 to 142 J/mm², the mixed lower bainite and martensite austenite microstructure changed to granular bainite; further, the morphology of bainite ferrite gradually changed from lath to multilateral. Moreover, with the increase of EAD, the grain size was remarkably reduced because of the increasing austenitizing periods and temperature during thermal cycling. The average grain size was 1.56 µm, 3.98 µm, and 6.31 µm with EADs of 142 J/mm², 71 J/mm², and 47 J/mm², respectively. Yield strength and tensile strength of the SLM low-alloy steel increased with the increase in EAD; these values were significantly more than those of the alloys prepared by traditional methods. The microstructure of the SLM low-alloy steel samples is not uniform, and the inhomogeneity becomes more significant as EAD decreases. Simultaneously, when EAD decreases, the fracture mechanism changes from ductile to a mixture of ductile and brittle fracture; this is in contrast to the samples prepared by traditional methods. This study also found a stress concentration mechanism around large pores during plastic deformation that resulted in a brittle fracture. This indicates that large-sized pores significantly degrade the mechanical properties of the specimens. Full article

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11 pages, 3971 KiB

Open AccessArticle

Effect of Nanosilica on Mechanical Properties and Microstructure of PVA Fiber-Reinforced Geopolymer Composite (PVA-FRGC)

by Hasan Assaedi, Thamer Alomayri, Ayesha Siddika, Faiz Shaikh, Hatem Alamri, Subaer Subaer and It-Meng Low

Materials 2019, 12(21), 3624; https://doi.org/10.3390/ma12213624 - 04 Nov 2019

Cited by 29 | Viewed by 4694

Abstract

This paper presents the effects of various nanosilica (NS) contents on the mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PVA-FRGC). Microstructure analysis with X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the geopolymer composites. The results showed [...] Read more.

This paper presents the effects of various nanosilica (NS) contents on the mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PVA-FRGC). Microstructure analysis with X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the geopolymer composites. The results showed that the mechanical properties in terms of compressive strength, impact strength, and flexural behavior were improved due to the addition of NS to the PVA-FRGC. The optimum NS content was 1.0 to 2.0 wt%, which exhibited highest improvement in the above mechanical properties. Microstructure analysis showed that the addition of NS up to an optimum level densified the microstructure of the matrix as well as the PVA fiber–geopolymer matrix interface. Full article

(This article belongs to the Special Issue Advances in Natural Fiber Reinforced Polymer and Geopolymer Composites: Synthesis, Applications and Future Directions)

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19 pages, 3720 KiB

Open AccessArticle

Model for Predicting the Tortuosity of Transport Paths in Cement-Based Materials

by Tongning Cao, Lijuan Zhang, Guowen Sun, Caihui Wang, Ying Zhang, Na Yan and Aoxue Xu

Materials 2019, 12(21), 3623; https://doi.org/10.3390/ma12213623 - 04 Nov 2019

Cited by 9 | Viewed by 2220

Abstract

The tortuosity of the pore structure is an important factor affecting medium (water and harmful ions) transport in cement-based materials. In this study, a new tortuosity model was established to reveal the effect of aggregate size, morphology, and graded media on the transport [...] Read more.

The tortuosity of the pore structure is an important factor affecting medium (water and harmful ions) transport in cement-based materials. In this study, a new tortuosity model was established to reveal the effect of aggregate size, morphology, and graded media on the transport path in cement-based materials. Based on the stereological principle and the geometric algorithm, the distribution model of the ideal pebble and polygonal aggregate in cement-based materials was given first. Then, based on the image processing technology and MATLAB software, the morphology of the actual aggregate was also characterized to prove the similarity relationship between the ideal aggregate and actual aggregate. The reliability of the tortuosity model was verified by the mercury intrusion porosimetry test and data from other literature. Based on the tortuosity model, the influences of the aggregate particle shape parameters, hydration degree, and water-to-cement ratio on the tortuosity of the transport path were analyzed. Finally, the tortuosity model was further simplified to facilitate engineering application. Full article

(This article belongs to the Special Issue Concrete and Construction Materials)

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14 pages, 4616 KiB

Open AccessArticle

β-Si₃N₄ Microcrystals Prepared by Carbothermal Reduction-Nitridation of Quartz

by Meng Zhang, Zhi Chen, Juntong Huang, Saifang Huang, Zhihui Hu, Zhijun Feng, Qingming Xiong and Xibao Li

Materials 2019, 12(21), 3622; https://doi.org/10.3390/ma12213622 - 04 Nov 2019

Cited by 11 | Viewed by 2746

Abstract

Single phase β-Si₃N₄ with microcrystals was synthesized via carbothermal reduction-nitridation (CRN) of quartz and carbon coke powder as starting materials. The effects of reaction parameters, i.e., heating temperature, holding time, C/SiO₂ ratio, Fe₂O₃ additive and β-Si [...] Read more.

Single phase β-Si₃N₄ with microcrystals was synthesized via carbothermal reduction-nitridation (CRN) of quartz and carbon coke powder as starting materials. The effects of reaction parameters, i.e., heating temperature, holding time, C/SiO₂ ratio, Fe₂O₃ additive and β-Si₃N₄ seeds on the phase transformation and morphology of products were investigated and discussed. Rather than receiving a mixture of both α- and β- phases of Si₃N₄ in the products, we synthesized powders of β-Si₃N₄ single polymorph in this work. The mechanism for the CRN synthesis of β-Si₃N₄ from quartz and the formation mechanism of Fe₃Si droplets were discussed. We also firstly reported the formation of Fe₃Si Archimedean solids from a CRN process where Fe₂O₃ was introduced as additive. Comparing to the gear-like short columnar morphology observed in samples without β-Si₃N₄ seeding, the addition of β-Si₃N₄ seeds led to an elongated morphology of final products and much finer widths. In addition, the β-Si₃N₄ microcrystals exhibited a violet‒blue spectral emission range, which could be highly valuable for their future potential optoelectronic applications. Full article

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15 pages, 9447 KiB

Open AccessArticle

Cutting Characteristics for Sugar Maple Using Single Grit with Spherical Cone and Triangular Pyramid Geometries

by Jian Zhang, Bin Luo, Li Li and Hongguang Liu

Materials 2019, 12(21), 3621; https://doi.org/10.3390/ma12213621 - 04 Nov 2019

Cited by 8 | Viewed by 2038

Abstract

Abrasive belt sanding plays an important role in wood processing. The abrasive grits on the belt perform similar to small cutting tools with negative rake angles. In this study, a series of single-grit scratching tests were carried out on Sugar maple workpieces to [...] Read more.

Abrasive belt sanding plays an important role in wood processing. The abrasive grits on the belt perform similar to small cutting tools with negative rake angles. In this study, a series of single-grit scratching tests were carried out on Sugar maple workpieces to investigate the cutting characteristics of two different abrasive-grit shapes. The spherical cone grits had two kinds of included angles, and the triangular pyramid grits provided two cutting forms: one main cutting edge and two side cutting edges as well as two main cutting edges. Both scratching along and across the wood grain direction were conducted. In all cases, the material deformation and surface creation were analyzed, as well as cutting force. Several physical cutting models were established to help further understand the cutting mechanism. A new method was proposed to evaluate the energy consumption of single-grit scratching. The results showed that triangular pyramid grits with sharp cutting edges could sever wood fibers more efficiently, while spherical cone grits are prone to make material plastic deformation mainly manifested as superficial densification and pile-up. When scratching along the wood grain, the triangular pyramid grit with two main cutting edges showed the best cutting performance with better surface quality. It was also shown that the cutting force ratio of spherical cone grits was apparently less than that of triangular pyramid grits. The overall cutting power for spherical cone grits was remarkably higher than that for triangular pyramid grits for both scratching along and across the wood grain, which indicates that triangular pyramid grits have higher cutting efficiency and power utilization. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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13 pages, 5187 KiB

Open AccessArticle

Determination of Strain Properties of the Leather Semi-Finished Product and Moisture-Removing Materials of Compression Rolls

by Auezhan Amanov, Gayrat Bahadirov, Tileubay Amanov, Gerasim Tsoy and Ayder Nabiev

Materials 2019, 12(21), 3620; https://doi.org/10.3390/ma12213620 - 04 Nov 2019

Cited by 29 | Viewed by 2661

Abstract

The paper presents the results of experimental studies to determine the strain properties and characteristics of a chrome leather semi-finished product of middle-weight bovine hide by its topographic sections and the coatings of the processing compression rolls. The strain pressure equations of depend [...] Read more.

The paper presents the results of experimental studies to determine the strain properties and characteristics of a chrome leather semi-finished product of middle-weight bovine hide by its topographic sections and the coatings of the processing compression rolls. The strain pressure equations of depend on the topographic sections of a leather semi-finished product are obtained, and the results of experiments on the effect of a number of layers on the amount of pressed moisture are presented. A mathematical dependence of the pressed moisture from the leather semi-finished product is obtained under various pressure values, rates, and the number of skin layers with monchons. The influence of the number of layers of leather semi-finished products with moisture-removing materials (monchons) on the process of moisture extraction at their vertical feed on the base plate is determined. In this paper, the influence of the number of skin layers and moisture-removing materials (monchons) on the technological process of moisture extraction from wet leather semi-finished products at their vertical feed on a base plate is studied as well. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 1491 KiB

Open AccessArticle

Enzymatically Functionalized Composite Materials Based on Nanocellulose and Poly(Vinyl Alcohol) Cryogel and Possessing Antimicrobial Activity

by Aysel Aslanli, Nikolay Stepanov, Tatyana Razheva, Elena A. Podorozhko, Ilya Lyagin, Vladimir I. Lozinsky and Elena Efremenko

Materials 2019, 12(21), 3619; https://doi.org/10.3390/ma12213619 - 04 Nov 2019

Cited by 14 | Viewed by 3469

Abstract

In the present work, innovative composite biomaterials possessing bactericidal properties and based on the hexahistidine-tagged organophosphorus hydrolase (His₆-OPH) entrapped in the poly(vinyl alcohol) cryogel (PVA-CG)/bacterial cellulose (BC) were developed. His₆-OPH possesses lactonase activity, with a number of N-acyl homoserine [...] Read more.

In the present work, innovative composite biomaterials possessing bactericidal properties and based on the hexahistidine-tagged organophosphorus hydrolase (His₆-OPH) entrapped in the poly(vinyl alcohol) cryogel (PVA-CG)/bacterial cellulose (BC) were developed. His₆-OPH possesses lactonase activity, with a number of N-acyl homoserine lactones being the inducers of Gram-negative bacterial resistance. The enzyme can also be combined with various antimicrobial agents (antibiotics and antimicrobial peptides) to improve the efficiency of their action. In this study, such an effect was shown for composite biomaterials when His₆-OPH was entrapped in PVA-CG/BC together with β-lactam antibiotic meropenem or antimicrobial peptides temporin A and indolicidin. The residual catalytic activity of immobilized His₆-OPH was 60% or more in all the composite samples. In addition, the presence of BC filler in the PVA-CG composite resulted in a considerable increase in the mechanical strength and heat endurance of the polymeric carrier compared to the BC-free cryogel matrix. Such enzyme-containing composites could be interesting in the biomedical field to help overcome the problem of antibiotic resistance of pathogenic microorganisms. Full article

(This article belongs to the Special Issue Advanced Polymeric Biomaterials: Preparation, characterization and applications)

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15 pages, 8842 KiB

Open AccessArticle

Nanocomposites SnO₂/SiO₂:SiO₂ Impact on the Active Centers and Conductivity Mechanism

by Dayana Gulevich, Marina Rumyantseva, Artem Marikutsa, Tatyana Shatalova, Elizaveta Konstantinova, Evgeny Gerasimov and Alexander Gaskov

Materials 2019, 12(21), 3618; https://doi.org/10.3390/ma12213618 - 04 Nov 2019

Cited by 8 | Viewed by 2450

Abstract

This paper is focused on the effect of the stabilizing component SiO₂ on the type and concentration of active sites in SnO₂/SiO₂ nanocomposites compared with nanocrystalline SnO₂. Previously, we found that SnO₂/SiO₂ nanocomposites show [...] Read more.

This paper is focused on the effect of the stabilizing component SiO₂ on the type and concentration of active sites in SnO₂/SiO₂ nanocomposites compared with nanocrystalline SnO₂. Previously, we found that SnO₂/SiO₂ nanocomposites show better sensor characteristics in CO detection (lower detection limit, higher sensor response, and shorter response time) compared to pure SnO₂ in humid air conditions. Nanocomposites SnO₂/SiO₂ synthesized using the hydrothermal method were characterized by low temperature nitrogen adsorption, XRD, energy dispersive X-ray spectroscopy (EDX), thermo-programmed reduction with hydrogen (TPR-H₂), IR-, and electron-paramagnetic resonance (EPR)-spectroscopy methods. The electrophysical properties of SnO₂ and SnO₂/SiO₂ nanocomposites were studied depending on the oxygen partial pressure in the temperature range of 200–400 °C. The introduction of SiO₂ results in an increase in the concentration of paramagnetic centers Sn³⁺ and the amount of surface hydroxyl groups and chemisorbed oxygen and leads to a decrease in the negative charge on chemisorbed oxygen species. The temperature dependences of the conductivity of SnO₂ and SnO₂/SiO₂ nanocomposites are linearized in Mott coordinates, which may indicate the contribution of the hopping mechanism with a variable hopping distance over local states. Full article

(This article belongs to the Special Issue Metal Oxide Semiconductors for Gas Sensor Applications)

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10 pages, 6549 KiB

Open AccessArticle

Deformation and Compressive Strength of Steel Fiber Reinforced MgO Concrete

by Feifei Jiang, Zhongyang Mao, Min Deng and Dawang Li

Materials 2019, 12(21), 3617; https://doi.org/10.3390/ma12213617 - 04 Nov 2019

Cited by 12 | Viewed by 2927

Abstract

To reduce the cracking caused by shrinkage and avoid the brittle behavior of concrete, MgO expansion agent and steel fibers were used in this paper. Firstly, the effect of MgO and steel fibers on the compressive strength of concrete was compared. The results [...] Read more.

To reduce the cracking caused by shrinkage and avoid the brittle behavior of concrete, MgO expansion agent and steel fibers were used in this paper. Firstly, the effect of MgO and steel fibers on the compressive strength of concrete was compared. The results showed that the compressive strength of steel fibers reinforced concrete (SC) and steel fiber reinforced MgO concrete (SMC) was significantly improved. Compared with ordinary concrete (OC), SMC’s 28 days compressive strength increased by 19.8%. Secondly, the influence of MgO and steel fibers with different contents on the self-volumetric deformation of concrete was compared through the experiment. The results showed that as a result of the hydration expansion of MgO, MC and SMC both showed obvious expansion, and their 190 days expansion was 335

μ ε

and 288

μ ε

, respectively. Lastly, through a scanning electron microscope (SEM) test, it was found that the constraint effect of steel fibers changed the expansion mode of MgO from outward expansion to inward extrusion, thus improving the interfacial bond strength of concrete. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Concrete Composites)

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12 pages, 1531 KiB

Open AccessArticle

Investigation of AgInS₂/ZnS Quantum Dots by Magnetic Circular Dichroism Spectroscopy

by Yulia Gromova, Anastasiia Sokolova, Danil Kurshanov, Ivan Korsakov, Victoria Osipova, Sergei Cherevkov, Aliaksei Dubavik, Vladimir Maslov, Tatiana Perova, Yurii Gun’ko, Alexander Baranov and Anatoly Fedorov

Materials 2019, 12(21), 3616; https://doi.org/10.3390/ma12213616 - 04 Nov 2019

Cited by 15 | Viewed by 4722

Abstract

Over recent years, quantum dots (QDs) based on ternary metal dichalcogenides have attracted a lot of attention due to their unique properties and a range of potential applications. Here, we review the latest studies on the optical properties of AgInS₂/ZnS QDs [...] Read more.

Over recent years, quantum dots (QDs) based on ternary metal dichalcogenides have attracted a lot of attention due to their unique properties and a range of potential applications. Here, we review the latest studies on the optical properties of AgInS₂/ZnS QDs with emphasis on their theoretical modeling, and present our investigations of electronic transitions invisible in unstructured absorption spectra of AgInS₂/ZnS QDs. The analysis of the absorption, photoluminescence excitation (PLE), and magnetic circular dichroism (MCD) spectra of hydrophobic and hydrophilic AgInS₂/ZnS QDs of different sizes enables us to determine positions of electron transitions in these QDs. We demonstrate that the use of the second derivative of PLE spectra provides more unequivocal data on the position of the energy transitions compared with the second derivative of absorption spectra. Analysis of the MCD spectra reveals that the magnetic field induces energy level mixing in AgInS₂/ZnS QDs in contrast to the traditional Cd-based QDs, where MCD is associated only with removing degeneracy of the excited energy level. Full article

(This article belongs to the Special Issue Optical Characterization of Novel Composite and Optically Active Materials)

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19 pages, 8038 KiB

Open AccessArticle

Reactive Powder Concrete Mix Ratio and Steel Fiber Content Optimization under Different Curing Conditions

by Yunlong Zhang, Bin Wu, Jing Wang, Mo Liu and Xu Zhang

Materials 2019, 12(21), 3615; https://doi.org/10.3390/ma12213615 - 04 Nov 2019

Cited by 15 | Viewed by 3752

Abstract

In this paper, a practical reactive powder concrete mixture ratio is created on the basis of an orthogonal experiment. Previous studies have combined the compressive and splitting tensile strengths of four categories of reactive powder concrete (RPC) for major materials. These categories include [...] Read more.

In this paper, a practical reactive powder concrete mixture ratio is created on the basis of an orthogonal experiment. Previous studies have combined the compressive and splitting tensile strengths of four categories of reactive powder concrete (RPC) for major materials. These categories include water/binder ratio, silica fume volume content, sand/binder ratio, and dosage of fly ash volume. The optimal mixing proportion of each factor was determined by analyzing the compressive strength of the RPC matrix. For this purpose, steel fiber was used as a reinforcing agent. The compressive and splitting tensile strength test results of steel fiber RPC were analyzed by comparing compound, standard, and natural curing. This was conducted to explore the improvement effect of different steel fiber contents on compressive performance, especially tensile strength of the RPC matrix. According to the results, the optimal steel fiber content was found to be 4% under the three curing conditions. The effect of compound curing on early strength was found to be greater in RPC than by natural or standard curing. However, the effect of late improvement is not obvious. Although standard curing is slightly stronger than natural curing, the performance under the latter can still meet engineering requirements. Full article

(This article belongs to the Special Issue High and Ultra-High Performance Concrete for Sustainable Construction)

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22 pages, 9882 KiB

Open AccessArticle

Microwave-Assisted Synthesis of High-Energy Faceted TiO₂ Nanocrystals Derived from Exfoliated Porous Metatitanic Acid Nanosheets with Improved Photocatalytic and Photovoltaic Performance

by Yi-en Du, Xianjun Niu, Wanxi Li, Jing An, Yufang Liu, Yongqiang Chen, Pengfei Wang, Xiaojing Yang and Qi Feng

Materials 2019, 12(21), 3614; https://doi.org/10.3390/ma12213614 - 04 Nov 2019

Cited by 19 | Viewed by 3103

Abstract

A facile one-pot microwave-assisted hydrothermal synthesis of rutile TiO₂ quadrangular prisms with dominant {110} facets, anatase TiO₂ nanorods and square nanoprisms with co-exposed {101}/[111] facets, anatase TiO₂ nanorhombuses with co-exposed {101}/{010} facets, and anatase TiO₂ nanospindles with dominant {010} [...] Read more.

A facile one-pot microwave-assisted hydrothermal synthesis of rutile TiO₂ quadrangular prisms with dominant {110} facets, anatase TiO₂ nanorods and square nanoprisms with co-exposed {101}/[111] facets, anatase TiO₂ nanorhombuses with co-exposed {101}/{010} facets, and anatase TiO₂ nanospindles with dominant {010} facets were reported through the use of exfoliated porous metatitanic acid nanosheets as a precursor. The nanostructures and the formation reaction mechanism of the obtained rutile and anatase TiO₂ nanocrystals from the delaminated nanosheets were investigated. The transformation from the exfoliated metatitanic nanosheets with distorted hexagonal cavities to TiO₂ nanocrystals involved a dissolution reaction of the nanosheets, nucleation of the primary [TiO₆]⁸⁻ monomers, and the growth of rutile-type and anatase-type TiO₂ nuclei during the microwave-assisted hydrothermal reaction. In addition, the photocatalytic activities of the as-prepared anatase nanocrystals were evaluated through the photocatalytic degradation of typical carcinogenic and mutagenic methyl orange (MO) under UV-light irradiation at a normal temperature and pressure. Furthermore, the dye-sensitized solar cell (DSSC) performance of the synthesized anatase TiO₂ nanocrystals with various morphologies and crystal facets was also characterized. The {101}/[111]-faceted pH2.5-T175 nanocrystal showed the highest photocatalytic and photovoltaic performance compared to the other TiO₂ samples, which could be attributed mainly to its minimum particle size and maximum specific surface area. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Materials)

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