Materials

1546 KiB

Open AccessArticle

Diffusion and Interface Effects during Preparation of All-Solid Microstructured Fibers

by Kobelke Jens, Bierlich Jörg, Wondraczek Katrin, Aichele Claudia, Pan Zhiwen, Unger Sonja, Schuster Kay and Bartelt Hartmut

Materials 2014, 7(9), 6879-6892; https://doi.org/10.3390/ma7096879 - 25 Sep 2014

Cited by 7 | Viewed by 7372

Abstract

All-solid microstructured optical fibers (MOF) allow the realization of very flexible optical waveguide designs. They are prepared by stacking of doped silica rods or canes in complex arrangements. Typical dopants in silica matrices are germanium and phosphorus to increase the refractive index (RI), [...] Read more.

All-solid microstructured optical fibers (MOF) allow the realization of very flexible optical waveguide designs. They are prepared by stacking of doped silica rods or canes in complex arrangements. Typical dopants in silica matrices are germanium and phosphorus to increase the refractive index (RI), or boron and fluorine to decrease the RI. However, the direct interface contact of stacking elements often causes interrelated chemical reactions or evaporation during thermal processing. The obtained fiber structures after the final drawing step thus tend to deviate from the targeted structure risking degrading their favored optical functionality. Dopant profiles and design parameters (e.g., the RI homogeneity of the cladding) are controlled by the combination of diffusion and equilibrium conditions of evaporation reactions. We show simulation results of diffusion and thermal dissociation in germanium and fluorine doped silica rod arrangements according to the monitored geometrical disturbances in stretched canes or drawn fibers. The paper indicates geometrical limits of dopant structures in sub-µm-level depending on the dopant concentration and the thermal conditions during the drawing process. The presented results thus enable an optimized planning of the preform parameters avoiding unwanted alterations in dopant concentration profiles or in design parameters encountered during the drawing process. Full article

(This article belongs to the Special Issue New Materials and Processing Methods for Microstructured Optical Fibres)

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496 KiB

Open AccessArticle

A Novel Exploration of a Combination of Gambogic Acid with TiO₂ Nanofibers: The Photodynamic Effect for HepG2 Cell Proliferation

by Jingyuan Li, Xuemei Wang, Yixiang Shao, Xiaohua Lu and Baoan Chen

Materials 2014, 7(9), 6865-6878; https://doi.org/10.3390/ma7096865 - 24 Sep 2014

Cited by 12 | Viewed by 6649

Abstract

As a good photosensitizer, TiO₂ nanomaterials show potential biomedical applications, such as drug carriers or enhancers in photodynamic therapy. In this contribution, novel nanocomposites through the blending of TiO₂ nanofibers with the active compound, gambogic acid (GA), were explored, and the [...] Read more.

As a good photosensitizer, TiO₂ nanomaterials show potential biomedical applications, such as drug carriers or enhancers in photodynamic therapy. In this contribution, novel nanocomposites through the blending of TiO₂ nanofibers with the active compound, gambogic acid (GA), were explored, and the results showed that GA could inhibit cancer cell proliferation in a time-dependent and dose-dependent manner, inducing apoptosis and cell cycle arrest at the G0/G1 phase in HepG2 cells. It is evident that after the GA-TiO₂ nanocomposites were cultured with the cancer cells, the cooperation effect could effectively enhance the cytotoxicity of GA for HepG2 cells. Meanwhile, if activated by UV irradiation, under the presence of GA-TiO₂ nanocomposites, this would lead to significant apoptosis and necrosis for HepG2 cells with a photodynamic therapy (PDT) effect. Associated with the controlled drug-release from these nanocomposites, TiO₂ nanofibers could readily cut down the drug consumption in HepG2 cells and reduce the side-effect for the normal cells and tissue, which may be further utilized in the therapeutic alliance for cancer therapy. Full article

(This article belongs to the Special Issue Materials for Drug Delivery)

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639 KiB

Open AccessArticle

Evaluation of Binding Effects in Wood Flour Board Containing Ligno-Cellulose Nanofibers

by Yoichi Kojima, Akiko Isa, Hikaru Kobori, Shigehiko Suzuki, Hirokazu Ito, Rie Makise and Masaki Okamoto

Materials 2014, 7(9), 6853-6864; https://doi.org/10.3390/ma7096853 - 22 Sep 2014

Cited by 29 | Viewed by 6932

Abstract

Wood-based materials are used extensively in residual construction worldwide. Most of the adhesives used in wood-based materials are derived from fossil resources, and some are not environmentally friendly. This study explores nanofiber technology as an alternative to such adhesives. Previous studies have shown [...] Read more.

Wood-based materials are used extensively in residual construction worldwide. Most of the adhesives used in wood-based materials are derived from fossil resources, and some are not environmentally friendly. This study explores nanofiber technology as an alternative to such adhesives. Previous studies have shown that the three-dimensional binding effects of cellulose nanofiber (CNF), when mixed with wood flour, can significantly improve the physical and mechanical properties of wood flour board. In this study, ligno-cellulose nanofibers (LCNF) were fabricated by wet disk milling of wood flour. Composite boards of wood flour and LCNF were produced to investigate the binding effect(s) of LCNF. The fabrication of LCNF by disk milling was simple and effective, and its incorporation into wood flour board significantly enhanced the physical and mechanical properties of the board. Full article

(This article belongs to the Special Issue Advances in Cellulosic Materials 2014)

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2283 KiB

Open AccessCommunication

A Label-Free Immunosensor for IgG Based on an Extended-Gate Type Organic Field Effect Transistor

by Tsukuru Minamiki, Tsuyoshi Minami, Ryoji Kurita, Osamu Niwa, Shin-ichi Wakida, Kenjiro Fukuda, Daisuke Kumaki and Shizuo Tokito

Materials 2014, 7(9), 6843-6852; https://doi.org/10.3390/ma7096843 - 22 Sep 2014

Cited by 54 | Viewed by 10630

Abstract

A novel biosensor for immunoglobulin G (IgG) detection based on an extended-gate type organic field effect transistor (OFET) has been developed that possesses an anti-IgG antibody on its extended-gate electrode and can be operated below 3 V. The titration results from the target [...] Read more.

A novel biosensor for immunoglobulin G (IgG) detection based on an extended-gate type organic field effect transistor (OFET) has been developed that possesses an anti-IgG antibody on its extended-gate electrode and can be operated below 3 V. The titration results from the target IgG in the presence of a bovine serum albumin interferent, clearly exhibiting a negative shift in the OFET transfer curve with increasing IgG concentration. This is presumed to be due an interaction between target IgG and the immobilized anti-IgG antibody on the extended-gate electrode. As a result, a linear range from 0 to 10 µg/mL was achieved with a relatively low detection limit of 0.62 µg/mL (=4 nM). We believe that these results open up opportunities for applying extended-gate-type OFETs to immunosensing. Full article

(This article belongs to the Special Issue Organic Transistor)

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570 KiB

Open AccessArticle

Cold-Curing Structural Epoxy Resins: Analysis of the Curing Reaction as a Function of Curing Time and Thickness

by Carola Esposito Corcione, Fabrizio Freuli and Mariaenrica Frigione

Materials 2014, 7(9), 6832-6842; https://doi.org/10.3390/ma7096832 - 22 Sep 2014

Cited by 33 | Viewed by 8566

Abstract

The curing reaction of a commercial cold-curing structural epoxy resin, specifically formulated for civil engineering applications, was analyzed by thermal analysis as a function of the curing time and the sample thickness. Original and remarkable results regarding the effects of curing time on [...] Read more.

The curing reaction of a commercial cold-curing structural epoxy resin, specifically formulated for civil engineering applications, was analyzed by thermal analysis as a function of the curing time and the sample thickness. Original and remarkable results regarding the effects of curing time on the glass transition temperature and on the residual heat of reaction of the cold-cured epoxy were obtained. The influence of the sample thickness on the curing reaction of the cold-cured resin was also deeply investigated. A highly exothermal reaction, based on a self-activated frontal polymerization reaction, was supposed and verified trough a suitable temperature signal acquisition system, specifically realized for this measurement. This is one of the first studies carried out on the curing behavior of these peculiar cold-cured epoxy resins as a function of curing time and thickness. Full article

(This article belongs to the Section Advanced Composites)

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Open AccessArticle

Optimization of Aluminum Stressed Skin Panels in Offshore Applications

by Dianne Van Hove and Frans Soetens

Materials 2014, 7(9), 6811-6831; https://doi.org/10.3390/ma7096811 - 19 Sep 2014

Cited by 2 | Viewed by 7744

Abstract

Since the introduction of general European rules for the design of aluminium structures, specific rules for the design of aluminum stressed skin panels are available. These design rules have been used for the optimization of two extrusion products: one for explosions and wind [...] Read more.

Since the introduction of general European rules for the design of aluminium structures, specific rules for the design of aluminum stressed skin panels are available. These design rules have been used for the optimization of two extrusion products: one for explosions and wind load governing and one for explosions and floor load governing. The optimized extrusions fulfill Class 3 section properties, leading to weight reductions up to 25% of regularly-used shear panel sections. When the design is based on Class 4 section properties, even more weight reduction may be reached. The typical failure mode of the optimized stressed skin panels depends on the applied height of the hat stiffeners. For sections using relatively high hat stiffeners, failure is introduced by yielding of the heat-affected zone. For this type of cross-section, Eurocode 9 design rules and numerical calculations show very good agreement. For sections using relatively low hat stiffeners, failure is introduced by global buckling. For this type of cross-section, Eurocode 9 gives rather conservative results. Full article

(This article belongs to the Special Issue Selected Papers from the International Aluminium Conference (INALCO) 2013)

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1287 KiB

Open AccessArticle

Fabrication of Aluminum Foam-Filled Thin-Wall Steel Tube by Friction Welding and Its Compression Properties

by Yoshihiko Hangai, Masaki Saito, Takao Utsunomiya, Soichiro Kitahara, Osamu Kuwazuru and Nobuhiro Yoshikawa

Materials 2014, 7(9), 6796-6810; https://doi.org/10.3390/ma7096796 - 19 Sep 2014

Cited by 26 | Viewed by 10776

Abstract

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such [...] Read more.

Aluminum foam has received considerable attention in various fields and is expected to be used as an engineering material owing to its high energy absorption properties and light weight. To improve the mechanical properties of aluminum foam, combining it with dense tubes, such as aluminum foam-filled tubes, was considered necessary. In this study, an aluminum foam-filled steel tube, which consisted of ADC12 aluminum foam and a thin-wall steel tube, was successfully fabricated by friction welding. It was shown that a diffusion bonding layer with a thickness of approximately 10 μm was formed, indicating that strong bonding between the aluminum foam and the steel tube was realized. By the X-ray computed tomography observation of pore structures, the fabrication of an aluminum foam-filled tube with almost uniform pore structures over the entire specimen was confirmed. In addition, it was confirmed that the aluminum foam-filled steel tube exhibited mechanical properties superior to those of the ADC12 aluminum foam and steel tube. This is considered to be attributed to the combination of the aluminum foam and steel tube, which particularly prevents the brittle fracture and collapse of the ADC12 foam by the steel tube, along with the strong metal bonding between the aluminum foam and the steel tube. Full article

(This article belongs to the Section Porous Materials)

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Open AccessArticle

Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement

by Lucas C. Rodriguez, Jonathan Chari, Shant Aghyarian, Izabelle M. Gindri, Victor Kosmopoulos and Danieli C. Rodrigues

Materials 2014, 7(9), 6779-6795; https://doi.org/10.3390/ma7096779 - 19 Sep 2014

Cited by 26 | Viewed by 7383

Abstract

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, [...] Read more.

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, calcium phosphate cements prepared with hydroxyapatite, brushite or tricalcium phosphates have been introduced with rather unsuccessful results due to increased cement viscosity, poor handling and reduced mechanical performance. This has limited the use of such cements in applications requiring delivery through small cannulas and in load bearing. The goal of this study is to design an alternative cement system that can better accommodate calcium-phosphate additives while preserving cement rheological properties and performance. In the present work, a number of brushite-filled two-solution bone cements were prepared and characterized by studying their complex viscosity-versus-test frequency, extrusion stress, clumping tendency during injection through a syringe, extent of fill of a machined void in cortical bone analog specimens, and compressive strength. The addition of brushite into the two-solution cement formulations investigated did not affect the pseudoplastic behavior and handling properties of the materials as demonstrated by rheological experiments. Extrusion stress was observed to vary with brushite concentration with values lower or in the range of control PMMA-based cements. The materials were observed to completely fill pre-formed voids in bone analog specimens. Cement compressive strength was observed to decrease with increasing concentration of fillers; however, the materials exhibited high enough strength for consideration in load bearing applications. The results indicated that partially substituting the PMMA phase of the two-solution cement with brushite at a 40% by mass concentration provided the best combination of the properties investigated. This alternative material may find applications in systems requiring highly injectable and viscous cements such as in the treatment of spinal fractures and bone defects. Full article

(This article belongs to the Section Biomaterials)

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1184 KiB

Open AccessArticle

Sol-Gel Synthesis and Antioxidant Properties of Yttrium Oxide Nanocrystallites Incorporating P-123

by Rebeca Mellado-Vázquez, Margarita García-Hernández, Arturo López-Marure, Perla Yolanda López-Camacho, Ángel De Jesús Morales-Ramírez and Hiram Isaac Beltrán-Conde

Materials 2014, 7(9), 6768-6778; https://doi.org/10.3390/ma7096768 - 19 Sep 2014

Cited by 32 | Viewed by 7316

Abstract

Yttrium oxide (Y₂O₃) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems [...] Read more.

Yttrium oxide (Y₂O₃) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems were heat-treated at temperatures from 700 °C to 900 °C. Systems at 900 °C were prepared in the presence and absence of P-123 using different molar ratios (P-123:Y = 1:1 and 2:1). Fourier transform infrared spectroscopy (FTIR) results revealed a characteristic absorption band of Y–O vibrations typical of Y₂O₃ matrix. The structural phase was analyzed by X-ray diffraction (XRD), showing the characteristic cubic phase in all systems. The diffraction peak that presented the major intensity corresponded to the sample prepared from yttrium chloride incorporating P-123 in a molar ratio of P-123:Y = 2:1 at 900 °C. Crystallites sizes were determined by Scherrer equation as between 21 nm and 32 nm. Antioxidant properties were estimated by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assays; the results are discussed. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International e-Conference on Materials)

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2772 KiB

Open AccessArticle

Matrix Structure Evolution and Nanoreinforcement Distribution in Mechanically Milled and Spark Plasma Sintered Al-SiC Nanocomposites

by Nouari Saheb, Ismaila Kayode Aliyu, Syed Fida Hassan and Nasser Al-Aqeeli

Materials 2014, 7(9), 6748-6767; https://doi.org/10.3390/ma7096748 - 19 Sep 2014

Cited by 28 | Viewed by 7319

Abstract

Development of homogenous metal matrix nanocomposites with uniform distribution of nanoreinforcement, preserved matrix nanostructure features, and improved properties, was possible by means of innovative processing techniques. In this work, Al-SiC nanocomposites were synthesized by mechanical milling and consolidated through spark plasma sintering. Field [...] Read more.

Development of homogenous metal matrix nanocomposites with uniform distribution of nanoreinforcement, preserved matrix nanostructure features, and improved properties, was possible by means of innovative processing techniques. In this work, Al-SiC nanocomposites were synthesized by mechanical milling and consolidated through spark plasma sintering. Field Emission Scanning Electron Microscope (FE-SEM) with Energy Dispersive X-ray Spectroscopy (EDS) facility was used for the characterization of the extent of SiC particles’ distribution in the mechanically milled powders and spark plasma sintered samples. The change of the matrix crystallite size and lattice strain during milling and sintering was followed through X-ray diffraction (XRD). The density and hardness of the developed materials were evaluated as function of SiC content at fixed sintering conditions using a densimeter and a digital microhardness tester, respectively. It was found that milling for 24 h led to uniform distribution of SiC nanoreinforcement, reduced particle size and crystallite size of the aluminum matrix, and increased lattice strain. The presence and amount of SiC reinforcement enhanced the milling effect. The uniform distribution of SiC achieved by mechanical milling was maintained in sintered samples. Sintering led to the increase in the crystallite size of the aluminum matrix; however, it remained less than 100 nm in the composite containing 10 wt.% SiC. Density and hardness of sintered nanocomposites were reported and compared with those published in the literature. Full article

(This article belongs to the Section Advanced Materials Characterization)

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1128 KiB

Open AccessArticle

Preparation and Characterization of Lignocellulosic Oil Sorbent by Hydrothermal Treatment of Populus Fiber

by Yue Zhang, Sheng Yang, Jian-Quan Wu, Tong-Qi Yuan and Run-Cang Sun

Materials 2014, 7(9), 6733-6747; https://doi.org/10.3390/ma7096733 - 18 Sep 2014

Cited by 33 | Viewed by 8658

Abstract

This study is aimed at achieving the optimum conditions of hydrothermal treatment and acetylation of Populus fiber to improve its oil sorption capacity (OSC) in an oil-water mixture. The characteristics of the hydrolyzed and acetylated fibers were comparatively investigated by FT-IR, CP-MAS ¹³ [...] Read more.

This study is aimed at achieving the optimum conditions of hydrothermal treatment and acetylation of Populus fiber to improve its oil sorption capacity (OSC) in an oil-water mixture. The characteristics of the hydrolyzed and acetylated fibers were comparatively investigated by FT-IR, CP-MAS ¹³C-NMR, SEM and TGA. The optimum conditions of the hydrothermal treatment and acetylation were obtained at170 °C for 1 h and 120 °C for 2 h, respectively. The maximum OSC of the hydrolyzed fiber (16.78 g/g) was slightly lower than that of the acetylated fiber (21.57 g/g), but they were both higher than the maximum OSC of the unmodified fiber (3.94 g/g). In addition, acetylation after hydrothermal treatment for the Populus fiber was unnecessary as the increment of the maximum OSC was only 3.53 g/g. The hydrolyzed and the acetylated Populus fibers both displayed a lumen orifice enabling a high oil entrapment. The thermal stability of the modified fibers was shown to be increased in comparison with that of the raw fiber. The hydrothermal treatment offers a new approach to prepare lignocellulosic oil sorbent. Full article

(This article belongs to the Special Issue Advances in Cellulosic Materials 2014)

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Open AccessReview

Review on Polymers for Thermoelectric Applications

by Mario Culebras, Clara M. Gómez and Andrés Cantarero

Materials 2014, 7(9), 6701-6732; https://doi.org/10.3390/ma7096701 - 18 Sep 2014

Cited by 192 | Viewed by 18579

Abstract

In this review, we report the state-of-the-art of polymers in thermoelectricity. Classically, a number of inorganic compounds have been considered as the best thermoelectric materials. Since the prediction of the improvement of the figure of merit by means of electronic confinement in 1993, [...] Read more.

In this review, we report the state-of-the-art of polymers in thermoelectricity. Classically, a number of inorganic compounds have been considered as the best thermoelectric materials. Since the prediction of the improvement of the figure of merit by means of electronic confinement in 1993, it has been improved by a factor of 3–4. In the mean time, organic materials, in particular intrinsically conducting polymers, had been considered as competitors of classical thermoelectrics, since their figure of merit has been improved several orders of magnitude in the last few years. We review here the evolution of the figure of merit or the power factor during the last years, and the best candidates to compete with inorganic materials. We also outline the best polymers to substitute classical thermoelectric materials and the advantages they present in comparison with inorganic systems. Full article

(This article belongs to the Special Issue New Energy Materials)

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3326 KiB

Open AccessArticle

Analysis of Pelletizing of Granulometric Separation Powder from Cork Industries

by Irene Montero, Teresa Miranda, Francisco José Sepúlveda, José Ignacio Arranz and Sergio Nogales

Materials 2014, 7(9), 6686-6700; https://doi.org/10.3390/ma7096686 - 18 Sep 2014

Cited by 10 | Viewed by 5951

Abstract

Cork industries generate a considerable amount of solid waste during their processing. Its management implies a problem for companies that should reconsider its reuse for other purposes. In this work, an analysis of pelletizing of granulometric separation powder, which is one of the [...] Read more.

Cork industries generate a considerable amount of solid waste during their processing. Its management implies a problem for companies that should reconsider its reuse for other purposes. In this work, an analysis of pelletizing of granulometric separation powder, which is one of the major wastes in cork industries and which presents suitable properties (as an raw material) for its thermal use, is studied. However, its characteristic heterogeneity, along with its low bulk density (which makes its storage and transportation difficult) are restrictive factors for its energy use. Therefore, its densified form is a real alternative in order to make the product uniform and guarantee its proper use in boiler systems. Thus, the cork pellets (from granulometric separation powder) in the study met, except for ash content specification, the specifications in standard European Norm EN-Plus (B) for its application as fuel for domestic use. Full article

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383 KiB

Open AccessArticle

Life Cycle Assessment for Proton Conducting Ceramics Synthesized by the Sol-Gel Process

by Soo-Sun Lee and Tae-Whan Hong

Materials 2014, 7(9), 6677-6685; https://doi.org/10.3390/ma7096677 - 16 Sep 2014

Cited by 5 | Viewed by 6157

Abstract

In this report, the environmental aspects of producing proton conducting ceramics are investigated by means of the environmental Life Cycle Assessment (LCA) method. The proton conducting ceramics BaZr_0.8Y_0.2O_3-δ (BZY), BaCe_0.9Y_0.1O_2.95 (BCY10), and Sr(Ce [...] Read more.

In this report, the environmental aspects of producing proton conducting ceramics are investigated by means of the environmental Life Cycle Assessment (LCA) method. The proton conducting ceramics BaZr_0.8Y_0.2O_3-δ (BZY), BaCe_0.9Y_0.1O_2.95 (BCY10), and Sr(Ce_0.9Zr_0.1)_0.95Yb_0.05O_3-δ (SCZY) were prepared by the sol-gel process. Their material requirements and environmental emissions were inventoried, and their energy requirements were determined, based on actual production data. This latter point makes the present LCA especially worthy of attention as a preliminary indication of future environmental impact. The analysis was performed according to the recommendations of ISO norms 14040 and obtained using the Gabi 6 software. The performance of the analyzed samples was also compared with each other. The LCA results for these proton conducting ceramics production processes indicated that the marine aquatic ecotoxicity potential (MAETP) made up the largest part, followed by fresh-water aquatic ecotoxicity potential (FAETP) and Human Toxicity Potential (HTP). The largest contribution was from energy consumption during annealing and calcinations steps. Full article

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Open AccessArticle

Sustained Release of Lidocaine from Solvent-Free Biodegradable Poly[(d,l)-Lactide-co-Glycolide] (PLGA): In Vitro and In Vivo Study

by Yi-Chuan Kau, Chia-Chih Liao, Ying-Chi Chen and Shih-Jung Liu

Materials 2014, 7(9), 6660-6676; https://doi.org/10.3390/ma7096660 - 16 Sep 2014

Cited by 13 | Viewed by 6770

Abstract

Local anesthetics are commonly used for pain relief by regional nerve blocking. In this study, we fabricated solvent-free biodegradable pellets to extend the duration of lidocaine release without any significant local or systemic toxicity levels. To manufacture the pellets, poly[(d,l)-lactide-co-glycolide] (PLGA) was first [...] Read more.

Local anesthetics are commonly used for pain relief by regional nerve blocking. In this study, we fabricated solvent-free biodegradable pellets to extend the duration of lidocaine release without any significant local or systemic toxicity levels. To manufacture the pellets, poly[(d,l)-lactide-co-glycolide] (PLGA) was first pre-mixed with lidocaine powder into different ratios. The powder mixture was then compressed with a mold (diameter of 1, 5, 8 or 10 mm) and sintered at 65 °C to form pellets. The in vitro release study showed that the lidocaine/PLGA pellets exhibited a tri-phase release behavior (a burst, a diffusion-controlled release and a degradation-dominated release) and reached completion around day 28. Scanning electron microscope (SEM) photos show that small channels could be found on the surfaces of the pellets on day 2. Furthermore, the polymer matrix swelled and fell apart on day 7, while the pellets became viscous after 10 days of in vitro elution. Perineural administration of the lidocaine/PLGA pellets produced anti-hypersensitivity effects lasting for at least 24 h in rats, significant when compared to the control group (a pure PLGA was pellet administered). In addition, no inflammation was detected within the nerve and in the neighboring muscle by histopathology. Full article

(This article belongs to the Section Biomaterials)

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Open AccessArticle

Experimental Investigation on Pore Structure Characterization of Concrete Exposed to Water and Chlorides

by Jun Liu, Kaifeng Tang, Qiwen Qiu, Dong Pan, Zongru Lei and Feng Xing

Materials 2014, 7(9), 6646-6659; https://doi.org/10.3390/ma7096646 - 16 Sep 2014

Cited by 54 | Viewed by 8560

Abstract

In this paper, the pore structure characterization of concrete exposed to deionised water and 5% NaCl solution was evaluated using mercury intrusion porosity (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of calcium leaching, fly ash incorporation, and chloride ions [...] Read more.

In this paper, the pore structure characterization of concrete exposed to deionised water and 5% NaCl solution was evaluated using mercury intrusion porosity (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of calcium leaching, fly ash incorporation, and chloride ions on the evolution of pore structure characteristics were investigated. The results demonstrate that: (i) in ordinary concrete without any fly ash, the leaching effect of the cement products is more evident than the cement hydration effect. From the experimental data, Ca(OH)₂ is leached considerably with the increase in immersion time. The pore structure of concrete can also be affected by the formation of an oriented structure of water in concrete materials; (ii) incorporation of fly ash makes a difference for the performance of concrete submersed in solutions as the total porosity and the pore connectivity can be lower. Especially when the dosage of fly ash is up to 30%, the pores with the diameter of larger than 100 nm show significant decrease. It demonstrates that the pore properties are improved by fly ash, which enhances the resistance against the calcium leaching; (iii) chlorides have a significant impact on microstructure of concrete materials because of the chemical interactions between the chlorides and cement hydrates. Full article

(This article belongs to the Section Porous Materials)

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Open AccessArticle

Corrosion Resistance of a Sand Particle-Modified Enamel Coating Applied to Smooth Steel Bars

by Fujian Tang, Genda Chen, Richard K. Brow and Michael L. Koenigstein

Materials 2014, 7(9), 6632-6645; https://doi.org/10.3390/ma7096632 - 15 Sep 2014

Cited by 11 | Viewed by 6719

Abstract

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The [...] Read more.

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO₂, CaCO₃ and MgCO₃. SEM images demonstrated that the enamel coating wetted well with the sand particles. However, a weak enamel coating zone was formed around the sand particles due to concentrated air bubbles, leading to micro-cracks as hydrogen gas pressure builds up and exceeds the tensile strength of the weak zone. As a result, the addition of sand particles into the enamel coating reduced both the coating and corrosion resistances. Full article

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Open AccessArticle

Surface Chloride Concentration of Concrete under Shallow Immersion Conditions

by Jun Liu, Kaifeng Tang, Dong Pan, Zongru Lei, Weilun Wang and Feng Xing

Materials 2014, 7(9), 6620-6631; https://doi.org/10.3390/ma7096620 - 15 Sep 2014

Cited by 26 | Viewed by 7139

Abstract

Deposition of chloride ions in the surface layer of concrete is investigated in this study. In real concrete structure, chloride ions from the service environment can penetrate into concrete and deposit in the surface layer, to form the boundary condition for further diffusion [...] Read more.

Deposition of chloride ions in the surface layer of concrete is investigated in this study. In real concrete structure, chloride ions from the service environment can penetrate into concrete and deposit in the surface layer, to form the boundary condition for further diffusion towards the interior. The deposit amount of chloride ions in the surface layer is normally a function of time, rather than a constant. In the experimental investigation, concrete specimens with different mix proportions are immersed in NaCl solution with a mass concentration of 5%, to simulate the shallow immersion condition in sea water, and the surface chloride concentrations are measured at different ages. It is found that the surface chloride concentration increases following the increasing immersion durations, and varies from a weight percentage of 0.161%–0.781% in concretes with different mix proportions. The w/c (water-to-cement ratio) influences the surface chloride concentration significantly, and the higher the w/c is, the higher the surface chloride concentration will be, at the same age. However, following the prolonging of immersion duration, the difference in surface chloride concentration induced by w/c becomes smaller and smaller. The incorporation of fly ash leads to higher surface chloride concentration. The phenomena are explained based on pore structure analyses. Full article

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Open AccessArticle

Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel

by Yanjun Guo, Jincheng Hu, Jin Li, Laizhu Jiang, Tianwei Liu and Yanping Wu

Materials 2014, 7(9), 6604-6619; https://doi.org/10.3390/ma7096604 - 12 Sep 2014

Cited by 59 | Viewed by 8879

Abstract

The effect of annealing temperature (1000–1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force [...] Read more.

The effect of annealing temperature (1000–1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and potentiostatic critical pitting temperature (CPT). The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP). The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN) of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN. Full article

(This article belongs to the Special Issue Corrosion of Materials)

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798 KiB

Open AccessArticle

Optical Absorption and Visible Photoluminescence from Thin Films of Silicon Phthalocyanine Derivatives

by Arturo Rodríguez Gómez, Carlos Moises Sánchez-Hernández, Ilán Fleitman-Levin, Jesús Arenas-Alatorre, Juan Carlos Alonso-Huitrón and María Elena Sánchez Vergara

Materials 2014, 7(9), 6585-6603; https://doi.org/10.3390/ma7096585 - 12 Sep 2014

Cited by 37 | Viewed by 9188

Abstract

The interest of microelectronics industry in new organic compounds for the manufacture of luminescent devices has increased substantially in the last decade. In this paper, we carried out a study of the usage feasibility of three organic bidentate ligands (2,6-dihydroxyanthraquinone, anthraflavic acid and [...] Read more.

The interest of microelectronics industry in new organic compounds for the manufacture of luminescent devices has increased substantially in the last decade. In this paper, we carried out a study of the usage feasibility of three organic bidentate ligands (2,6-dihydroxyanthraquinone, anthraflavic acid and potassium derivative salt of anthraflavic acid) for the synthesis of an organic semiconductor based in silicon phthalocyanines (SiPcs). We report the visible photoluminescence (PL) at room temperature obtained from thermal-evaporated thin films of these new materials. The surface morphology of these films was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM indicated that the thermal evaporation technique is an excellent resource in order to obtain low thin film roughness when depositing these kinds of compounds. Fourier transform infrared spectroscopy (FTIR) spectroscopy was employed to investigate possible changes in the intra-molecular bonds and to identify any evidence of crystallinity in the powder compounds and in the thin films after their deposition. FTIR showed that there was not any important change in the samples after the thermal deposition. The absorption coefficient (α) in the absorption region reveals non-direct transitions. Furthermore, the PL of all the investigated samples were observed with the naked eye in a bright background and also measured by a spectrofluorometer. The normalized PL spectra showed a Stokes shift ≈ 0.6 eV in two of our three samples, and no PL emission in the last one. Those results indicate that the Vis PL comes from a recombination of charge carriers between conduction band and valence band preceded by a non-radiative relaxation in the conduction band tails. Full article

(This article belongs to the Section Advanced Materials Characterization)

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513 KiB

Open AccessArticle

Valorization of Waste Obtained from Oil Extraction in Moringa Oleifera Seeds: Coagulation of Reactive Dyes in Textile Effluents

by Mercè Vilaseca, Víctor López-Grimau and Carmen Gutiérrez-Bouzán

Materials 2014, 7(9), 6569-6584; https://doi.org/10.3390/ma7096569 - 12 Sep 2014

Cited by 35 | Viewed by 11292

Abstract

Moringa oleifera seeds contain about 40% of highly valued oil due to its wide range of applications, from nutritional issues to cosmetics or biodiesel production. The extraction of Moringa oil generates a waste (65%–75% of seeds weight) which contains a water soluble protein [...] Read more.

Moringa oleifera seeds contain about 40% of highly valued oil due to its wide range of applications, from nutritional issues to cosmetics or biodiesel production. The extraction of Moringa oil generates a waste (65%–75% of seeds weight) which contains a water soluble protein able to be used either in drinking water clarification or wastewater treatment. In this paper, the waste of Moringa oleifera extraction was used as coagulant to remove five reactive dyes from synthetic textile effluents. This waste constitutes a natural coagulant which was demonstrated to be effective for the treatment of industrial reactive dyestuff effluents, characterized by alkaline pH, high NaCl content and hydrolyzed dyes. The coagulation yield increased at high NaCl concentration, whereas the pH did not show any significant effect on dye removal. Moringa oleifera showed better results for dye removal than the conventional treatment of coagulation-flocculation with FeCl₃ and polyelectrolyte. Treated water can be reused in new dyeing processes of cotton fabrics with high quality results. Full article

(This article belongs to the Special Issue Recycled Materials)

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2629 KiB

Open AccessReview

Theoretical Methods of Domain Structures in Ultrathin Ferroelectric Films: A Review

by Jianyi Liu, Weijin Chen, Biao Wang and Yue Zheng

Materials 2014, 7(9), 6502-6568; https://doi.org/10.3390/ma7096502 - 12 Sep 2014

Cited by 15 | Viewed by 17211

Abstract

This review covers methods and recent developments of the theoretical study of domain structures in ultrathin ferroelectric films. The review begins with an introduction to some basic concepts and theories (e.g., polarization and its modern theory, ferroelectric phase transition, domain formation, and finite [...] Read more.

This review covers methods and recent developments of the theoretical study of domain structures in ultrathin ferroelectric films. The review begins with an introduction to some basic concepts and theories (e.g., polarization and its modern theory, ferroelectric phase transition, domain formation, and finite size effects, etc.) that are relevant to the study of domain structures in ultrathin ferroelectric films. Basic techniques and recent progress of a variety of important approaches for domain structure simulation, including first-principles calculation, molecular dynamics, Monte Carlo simulation, effective Hamiltonian approach and phase field modeling, as well as multiscale simulation are then elaborated. For each approach, its important features and relative merits over other approaches for modeling domain structures in ultrathin ferroelectric films are discussed. Finally, we review recent theoretical studies on some important issues of domain structures in ultrathin ferroelectric films, with an emphasis on the effects of interfacial electrostatics, boundary conditions and external loads. Full article

(This article belongs to the Special Issue Ultra Thin Ferroic Materials)

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1385 KiB

Open AccessArticle

A Comparative Analysis of the Corrosive Effect of Artificial Saliva of Variable pH on DMLS and Cast Co-Cr-Mo Dental Alloy

by Tatjana Puskar, Danimir Jevremovic, Robert J. Williams, Dominic Eggbeer, Djordje Vukelic and Igor Budak

Materials 2014, 7(9), 6486-6501; https://doi.org/10.3390/ma7096486 - 11 Sep 2014

Cited by 51 | Viewed by 7902

Abstract

Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. [...] Read more.

Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM) samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS). The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments. Full article

(This article belongs to the Section Biomaterials)

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3965 KiB

Open AccessReview

Ultrathin Ferroelectric Films: Growth, Characterization, Physics and Applications

by Ying Wang, Weijin Chen, Biao Wang and Yue Zheng

Materials 2014, 7(9), 6377-6485; https://doi.org/10.3390/ma7096377 - 11 Sep 2014

Cited by 61 | Viewed by 22504

Abstract

Ultrathin ferroelectric films are of increasing interests these years, owing to the need of device miniaturization and their wide spectrum of appealing properties. Recent advanced deposition methods and characterization techniques have largely broadened the scope of experimental researches of ultrathin ferroelectric films, pushing [...] Read more.

Ultrathin ferroelectric films are of increasing interests these years, owing to the need of device miniaturization and their wide spectrum of appealing properties. Recent advanced deposition methods and characterization techniques have largely broadened the scope of experimental researches of ultrathin ferroelectric films, pushing intensive property study and promising device applications. This review aims to cover state-of-the-art experimental works of ultrathin ferroelectric films, with a comprehensive survey of growth methods, characterization techniques, important phenomena and properties, as well as device applications. The strongest emphasis is on those aspects intimately related to the unique phenomena and physics of ultrathin ferroelectric films. Prospects and challenges of this field also have been highlighted. Full article

(This article belongs to the Special Issue Ultra Thin Ferroic Materials)

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948 KiB

Open AccessArticle

Ferroelectric Switching of Vinylidene and Trifluoroethylene Copolymer Thin Films on Au Electrodes Modified with Self-Assembled Monolayers

by Naoto Tsutsumi, Tomotaka Kitano, Kenji Kinashi and Wataru Sakai

Materials 2014, 7(9), 6367-6376; https://doi.org/10.3390/ma7096367 - 8 Sep 2014

Cited by 6 | Viewed by 6832

Abstract

The ferroelectric switching characteristics of a vinylidene fluoride and trifluoroethylene copolymer were significantly changed via the chemical modification of a gold electrode with an alkanethiol self-assembled monolayer (SAM). The alkanethiol SAM-Au electrode successfully suppressed the leakage current (dark current) from the electrode to [...] Read more.

The ferroelectric switching characteristics of a vinylidene fluoride and trifluoroethylene copolymer were significantly changed via the chemical modification of a gold electrode with an alkanethiol self-assembled monolayer (SAM). The alkanethiol SAM-Au electrode successfully suppressed the leakage current (dark current) from the electrode to the bulk ferroelectric. Smaller leakage currents led to the formation of an effective electric field in the bulk ferroelectric. At switching cycles ranging from 10 to 100 kHz, significant changes in the ferroelectric properties were observed. At 100 kHz, a remanent polarization (Pr) of 68 mC·m⁻² was measured, whereas a very small Pr value of 2.4 mC·m⁻² was measured for the sample without a SAM. The switching speed of the SAM-Au electrode is as twice as fast as that of the unmodified electrode. A large potential barrier was formed via the insertion of a SAM between the Au electrode and the ferroelectric, effectively changing the ferroelectric switching characteristics. Full article

(This article belongs to the Special Issue Ultra Thin Ferroic Materials)

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919 KiB

Open AccessReview

A Review on Adsorption of Fluoride from Aqueous Solution

by Mirna Habuda-Stanić, Maja Ergović Ravančić and Andrew Flanagan

Materials 2014, 7(9), 6317-6366; https://doi.org/10.3390/ma7096317 - 5 Sep 2014

Cited by 221 | Viewed by 18141

Abstract

Fluoride is one of the anionic contaminants which is found in excess in surface or groundwater because of geochemical reactions or anthropogenic activities such as the disposal of industrial wastewaters. Among various methods used for defluoridation of water such as coagulation, precipitation, membrane [...] Read more.

Fluoride is one of the anionic contaminants which is found in excess in surface or groundwater because of geochemical reactions or anthropogenic activities such as the disposal of industrial wastewaters. Among various methods used for defluoridation of water such as coagulation, precipitation, membrane processes, electrolytic treatment, ion-exchange, the adsorption process is widely used. It offers satisfactory results and seems to be a more attractive method for the removal of fluoride in terms of cost, simplicity of design and operation. Various conventional and non-conventional adsorbents have been assessed for the removal of fluoride from water. In this review, a list of various adsorbents (oxides and hydroxides, biosorbents, geomaterials, carbonaceous materials and industrial products and by-products) and its modifications from literature are surveyed and their adsorption capacities under various conditions are compared. The effect of other impurities on fluoride removal has also been discussed. This survey showed that various adsorbents, especially binary and trimetal oxides and hydroxides, have good potential for the fluoride removal from aquatic environments. Full article

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1647 KiB

Open AccessArticle

Upgrade Recycling of Cast Iron Scrap Chips towards β-FeSi₂ Thermoelectric Materials

by Assayidatul Laila, Makoto Nanko and Masatoshi Takeda

Materials 2014, 7(9), 6304-6316; https://doi.org/10.3390/ma7096304 - 4 Sep 2014

Cited by 8 | Viewed by 7574

Abstract

The upgrade recycling of cast-iron scrap chips towards β-FeSi₂ thermoelectric materials is proposed as an eco-friendly and cost-effective production process. By using scrap waste from the machining process of cast-iron components, the material cost to fabricate β-FeSi₂ is reduced and the [...] Read more.

The upgrade recycling of cast-iron scrap chips towards β-FeSi₂ thermoelectric materials is proposed as an eco-friendly and cost-effective production process. By using scrap waste from the machining process of cast-iron components, the material cost to fabricate β-FeSi₂ is reduced and the industrial waste is recycled. In this study, β-FeSi₂ specimens obtained from cast iron scrap chips were prepared both in the undoped form and doped with Al and Co elements. The maximum figure of merit (ZT) indicated a thermoelectric performance of approximately 70% in p-type samples and nearly 90% in n-type samples compared to β-FeSi₂ prepared from pure Fe and other published studies. The use of cast iron scrap chips to produce β-FeSi₂ shows promise as an eco-friendly and cost-effective production process for thermoelectric materials. Full article

(This article belongs to the Special Issue Recycled Materials)

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696 KiB

Open AccessArticle

Anthracene Fibers Grown in a Microstructured Optical Fiber for X-ray Detection

by Stanton DeHaven, Russell Wincheski and Sacharia Albin

Materials 2014, 7(9), 6291-6303; https://doi.org/10.3390/ma7096291 - 3 Sep 2014

Cited by 5 | Viewed by 9009

Abstract

Anthracene fibers are grown inside a microstructured quartz matrix to form a multicore optical fiber for X-ray detection. A modified fiber growth method for single crystal anthracene from the melt via the Bridgman-Stockbarger technique is presented. The anthracene fiber is characterized by using [...] Read more.

Anthracene fibers are grown inside a microstructured quartz matrix to form a multicore optical fiber for X-ray detection. A modified fiber growth method for single crystal anthracene from the melt via the Bridgman-Stockbarger technique is presented. The anthracene fiber is characterized by using spectrophotometry, Raman spectroscopy, and X-ray diffraction. These results show the anthracene grown in fiber has high purity and a crystal structure similar to anthracene grown from liquid, vapor, and melt techniques. As an X-ray detector, the output is 12%–16% efficient between the energy ranges of 40 and 10 keV. The effect of materials and fiber processing are discussed. Full article

(This article belongs to the Special Issue New Materials and Processing Methods for Microstructured Optical Fibres)

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857 KiB

Open AccessArticle

Effects of Solvent Diols on the Synthesis of ZnFe₂O₄ Particles and Their Use as Heterogeneous Photo-Fenton Catalysts

by Chayene Gonçalves Anchieta, Adriano Cancelier, Marcio Antonio Mazutti, Sérgio Luiz Jahn, Raquel Cristine Kuhn, Andre Gündel, Osvaldo Chiavone-Filho and Edson Luiz Foletto

Materials 2014, 7(9), 6281-6290; https://doi.org/10.3390/ma7096281 - 3 Sep 2014

Cited by 52 | Viewed by 7648

Abstract

A solvothermal method was used to prepare zinc ferrite spinel oxide (ZnFe₂O₄) using ethylene glycol and 1,4 butanediol as solvent diols, and the influence of diols on the physical properties of ZnFe₂O₄ particles was investigated. The [...] Read more.

A solvothermal method was used to prepare zinc ferrite spinel oxide (ZnFe₂O₄) using ethylene glycol and 1,4 butanediol as solvent diols, and the influence of diols on the physical properties of ZnFe₂O₄ particles was investigated. The produced particles were characterized by X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption isotherms, and the catalytic activity for the organic pollutant decomposition by heterogeneous photo-Fenton reaction was investigated. Both solvents produced particles with cubic spinel structure. Microporous and mesoporous structures were obtained when ethylene glycol and 1,4 butanediol were used as diols, respectively. A higher pore volume and surface area, as well as a higher catalytic activity for the pollutant degradation were found when 1,4 butanediol was used as solvent. Full article

(This article belongs to the Section Porous Materials)

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2655 KiB

Open AccessArticle

Microstructural Analysis and Rheological Modeling of Asphalt Mixtures Containing Recycled Asphalt Materials

by Augusto Cannone Falchetto, Ki Hoon Moon and Michael P. Wistuba

Materials 2014, 7(9), 6254-6280; https://doi.org/10.3390/ma7096254 - 2 Sep 2014

Cited by 21 | Viewed by 8338

Abstract

The use of recycled materials in pavement construction has seen, over the years, a significant increase closely associated with substantial economic and environmental benefits. During the past decades, many transportation agencies have evaluated the effect of adding Reclaimed Asphalt Pavement (RAP), and, more [...] Read more.

The use of recycled materials in pavement construction has seen, over the years, a significant increase closely associated with substantial economic and environmental benefits. During the past decades, many transportation agencies have evaluated the effect of adding Reclaimed Asphalt Pavement (RAP), and, more recently, Recycled Asphalt Shingles (RAS) on the performance of asphalt pavement, while limits were proposed on the amount of recycled materials which can be used. In this paper, the effect of adding RAP and RAS on the microstructural and low temperature properties of asphalt mixtures is investigated using digital image processing (DIP) and modeling of rheological data obtained with the Bending Beam Rheometer (BBR). Detailed information on the internal microstructure of asphalt mixtures is acquired based on digital images of small beam specimens and numerical estimations of spatial correlation functions. It is found that RAP increases the autocorrelation length (ACL) of the spatial distribution of aggregates, asphalt mastic and air voids phases, while an opposite trend is observed when RAS is included. Analogical and semi empirical models are used to back-calculate binder creep stiffness from mixture experimental data. Differences between back-calculated results and experimental data suggest limited or partial blending between new and aged binder. Full article

(This article belongs to the Special Issue Recycled Materials)

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Materials, Volume 7, Issue 9 (September 2014) – 41 articles , Pages 6105-6892

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