Materials

283 KiB

Open AccessCorrection

Correction: Long-Term Soft Denture Lining Materials. Materials 2014, 7(8), 5816-5842

by Grzegorz Chladek, Jarosław Żmudzki and Jacek Kasperski

Materials 2015, 8(6), 3791-3792; https://doi.org/10.3390/ma8063791 - 23 Jun 2015

Cited by 1 | Viewed by 3460

In the published manuscript “Long-Term Soft Denture Lining Materials. Materials 2014, 7(8), 5816-5842” [1] we detected that in three places reference numbers were inserted incorrectly due to an error in the editing. [...] Full article

(This article belongs to the Section Biomaterials)

929 KiB

Open AccessArticle

Microstructural Study on Molten Marks of Fire-Causing Copper Wires

by Kuan-Heng Liu, Yung-Hui Shih, Guo-Ju Chen and Jaw-Min Chou

Materials 2015, 8(6), 3776-3790; https://doi.org/10.3390/ma8063776 - 22 Jun 2015

Cited by 17 | Viewed by 6185

Abstract

Although electrical fires constitute the greatest percentage of the main causes of building fires, the critical evidence used by fire investigators to identify electrical fires is not always convincing to the general public. In this study, we scrutinized the microstructures of fire-causing copper [...] Read more.

Although electrical fires constitute the greatest percentage of the main causes of building fires, the critical evidence used by fire investigators to identify electrical fires is not always convincing to the general public. In this study, we scrutinized the microstructures of fire-causing copper wires and simulated the external environmental conditions required for the formation of fire-causing arc beads. Our metallographic investigation revealed that the primary thermal dendrites of copper at the fire-causing arc bead grew parallel to one another, but in the opposite direction to the heat flow. We determined the relationships of the undercooling (∆T₀), the growth velocity (ν), and the primary spacing (λ) of the dendrites with respect to the electrical wire’s diameter. Accordingly, fire investigators can now identify fire-causing arc beads in terms of these metallographic characteristics, thereby providing clear scientific evidence for litigant judgments of electrical fires. Full article

(This article belongs to the Section Advanced Materials Characterization)

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832 KiB

Open AccessArticle

Liquid- and Gas-Phase Diffusion of Ferrocene in Thin Films of Metal-Organic Frameworks

by Wencai Zhou, Christof Wöll and Lars Heinke

Materials 2015, 8(6), 3767-3775; https://doi.org/10.3390/ma8063767 - 19 Jun 2015

Cited by 33 | Viewed by 7792

Abstract

The mass transfer of the guest molecules in nanoporous host materials, in particular in metal-organic frameworks (MOFs), is among the crucial features of their applications. By using thin surface-mounted MOF films in combination with a quartz crystal microbalance (QCM), the diffusion of ferrocene [...] Read more.

The mass transfer of the guest molecules in nanoporous host materials, in particular in metal-organic frameworks (MOFs), is among the crucial features of their applications. By using thin surface-mounted MOF films in combination with a quartz crystal microbalance (QCM), the diffusion of ferrocene vapor and of ethanolic and hexanic ferrocene solution in HKUST-1 was investigated. For the first time, liquid- and gas-phase diffusion in MOFs was compared directly in the identical sample. The diffusion coefficients are in the same order of magnitude (~10⁻¹⁶ m²·s⁻¹), whereas the diffusion coefficient of ferrocene in the empty framework is roughly 3-times smaller than in the MOF which is filled with ethanol or n-hexane. Full article

(This article belongs to the Special Issue Diffusion under Confinement in Nanopores)

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1193 KiB

Open AccessArticle

Revealing New Structural Insights from Surfactant Micelles through DLS, Microrheology and Raman Spectroscopy

by Samiul Amin, Steven Blake, Rachel C. Kennel and E. Neil Lewis

Materials 2015, 8(6), 3754-3766; https://doi.org/10.3390/ma8063754 - 19 Jun 2015

Cited by 28 | Viewed by 7423

Abstract

The correlation between molecular changes and microstructural evolution of rheological properties has been demonstrated for the first time in a mixed anionic/zwitterionic surfactant-based wormlike micellar system. Utilizing a novel combination of DLS-microrheology and Raman Spectroscopy, the effect of electrostatic screening on these properties [...] Read more.

The correlation between molecular changes and microstructural evolution of rheological properties has been demonstrated for the first time in a mixed anionic/zwitterionic surfactant-based wormlike micellar system. Utilizing a novel combination of DLS-microrheology and Raman Spectroscopy, the effect of electrostatic screening on these properties of anionic (SLES) and zwitterionic (CapB) surfactant mixtures was studied by modulating the NaCl concentration. As Raman Spectroscopy delivers information about the molecular structure and DLS-microrheology characterizes viscoelastic properties, the combination of data delivered allows for a deeper understanding of the molecular changes underlying the viscoelastic ones. The high frequency viscoelastic response obtained through DLS-microrheology has shown the persistence of the Maxwell fluid response for low viscosity solutions at high NaCl concentrations. The intensity of the Raman band at 170 cm⁻¹ exhibits very strong correlation with the viscosity variation. As this Raman band is assigned to hydrogen bonding, its variation with NaCl concentration additionally indicates differences in water structuring due to potential microstructural differences at low and high NaCl concentrations. The microstructural differences at low and high NaCl concentrations are further corroborated by persistence of a slow mode at the higher NaCl concentrations as seen through DLS measurements. The study illustrates the utility of the combined DLS, DLS-optical microrheology and Raman Spectroscopy in providing new molecular structural insights into the self-assembly process in complex fluids. Full article

(This article belongs to the Section Advanced Materials Characterization)

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1962 KiB

Open AccessArticle

Seismic Experimental Study on New-Type Composite Exterior Wallboard with Integrated Structural Function and Insulation

by Shaochun Ma and Nan Jiang

Materials 2015, 8(6), 3732-3753; https://doi.org/10.3390/ma8063732 - 19 Jun 2015

Cited by 15 | Viewed by 5190

Abstract

In order to evaluate the seismic performance of new-type composite exterior wallboard, a total of six exterior and interior wallboards were incorporated in the experiment of seismic performance. Seismic performance such as the stress process, damage mode, hysteresis and skeleton curve, load-carrying and [...] Read more.

In order to evaluate the seismic performance of new-type composite exterior wallboard, a total of six exterior and interior wallboards were incorporated in the experiment of seismic performance. Seismic performance such as the stress process, damage mode, hysteresis and skeleton curve, load-carrying and ductility coefficient, damping and energy dissipation, stiffness degradation as well as material strain of the exterior wallboards were analyzed with emphasis and compared with interior wallboards. Results of the experiment and analysis showed that both interior and exterior wallboards exhibited outstanding seismic performance. Due to the existence of insulation layer and externally bonded single gypsum board, the capacity of elastoplastic deformation and seismic energy dissipation of the exterior wallboards was improved and each seismic performance indicator of the exterior wallboards outperformed the interior wallboards. Full article

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Open AccessArticle

Properties of Cement Mortar by Use of Hot-Melt Polyamides as Substitute for Fine Aggregate

by Xiongzhou Yuan, Weiting Xu, Wei Sun, Feng Xing and Weilun Wang

Materials 2015, 8(6), 3714-3731; https://doi.org/10.3390/ma8063714 - 19 Jun 2015

Cited by 6 | Viewed by 5799

Abstract

This paper presents an experimental study on use of hot-melt polyamide (HMP) to prepare mortar specimens with improved crack healing and engineering properties. The role of HMP in the crack repairing of cement mortar subjected to several rounds of heat treatment was investigated. [...] Read more.

This paper presents an experimental study on use of hot-melt polyamide (HMP) to prepare mortar specimens with improved crack healing and engineering properties. The role of HMP in the crack repairing of cement mortar subjected to several rounds of heat treatment was investigated. Compatibility between HMP and hydraulic cement was investigated through X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) technology. Mortar specimens were prepared using standard cement mortar mixes with HMP at 1%, 3% and 5% (by volume) for fine aggregate substitute. After curing for 28 days, HMP specimens were subjected to heating at temperature of 160 °C for one, two, and three days and then natural cooling down to ambient temperature. Mechanical and durability properties of the heated HMP mortars were evaluated and compared with those of the corresponding mortars without heating. The microscopic observation of the interfacial transition zone (ITZ) of HMP mortar was conducted through environmental scanning electron microscopy (ESEM). Results reveal that incorporation of HMP improves the workability of the HMP/cement binder while leading to decrease in compressive strength and durability. The heated HMP mortars after exposure to heating for one, two, and three days exhibit no obvious change in compressive strength while presenting notable increase in flexural strength and durability compared with the corresponding mortars without heating. The XRD, FTIR and ESEM analyses indicate that no obvious chemical reaction occurs between HMP and hydraulic cement, and thus the self-repairing for interfacial micro-crack in HMP/cement composite system is ascribed to the physical adhesion of HMP to cement matrix rather than the chemical bonding between them. Full article

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Open AccessArticle

Mechanism of Filling and Feeding of Thin-Walled Structures during Gravity Casting

by Faguo Li, Jiao Zhang, Fenggang Bian, Yanan Fu, Yanling Xue, Fucheng Yin, Yu Xie, Yi Xu and Baode Sun

Materials 2015, 8(6), 3701-3713; https://doi.org/10.3390/ma8063701 - 19 Jun 2015

Cited by 6 | Viewed by 5572

Abstract

The filling and feeding of thin-walled structures in metal castings pose significant difficulties in manufacturing aerospace structural materials. Samples containing 2 mm and 5 mm thin-walled structures were designed to study the kinetics of filling. The microstructural evolution of the solidification of thin-walled [...] Read more.

The filling and feeding of thin-walled structures in metal castings pose significant difficulties in manufacturing aerospace structural materials. Samples containing 2 mm and 5 mm thin-walled structures were designed to study the kinetics of filling. The microstructural evolution of the solidification of thin-walled structures was studied with synchrotron X-radiation imaging. The formation of dendritic networks and the isotherm profiles of samples of different thickness were examined. The experimental results showed solidification microstructures of 2 mm and 5 mm thin-walled parts containing elongated equiaxed grains and normal equiaxed grains, respectively. The filling and feeding abilities of thin-walled parts were found to depend more on the wall thickness than on the pouring temperature. Full article

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

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952 KiB

Open AccessArticle

3D Printable Biophotopolymers for in Vivo Bone Regeneration

by Guenter Russmueller, Robert Liska, Juergen Stampfl, Christian Heller, Andreas Mautner, Karin Macfelda, Barbara Kapeller, Roman Lieber, Agnes Haider, Kathrin Mika, Christian Schopper, Christos Perisanidis, Rudolf Seemann and Doris Moser

Materials 2015, 8(6), 3685-3700; https://doi.org/10.3390/ma8063685 - 19 Jun 2015

Cited by 22 | Viewed by 6752

Abstract

The present study investigated two novel biophotopolymer classes that are chemically based on non-toxic poly (vinyl alcohol). These vinylesters and vinylcarbonates were compared to standard acrylates in vitro on MC3T3-E1 cells and in vivo in a small animal model. In vitro, both [...] Read more.

The present study investigated two novel biophotopolymer classes that are chemically based on non-toxic poly (vinyl alcohol). These vinylesters and vinylcarbonates were compared to standard acrylates in vitro on MC3T3-E1 cells and in vivo in a small animal model. In vitro, both vinylester and vinylcarbonate monomers showed about tenfold less cytotoxicity when compared to acrylates (IC₅₀: 2.922 mM and 2.392 mM vs. 0.201 mM) and at least threefold higher alkaline phosphatase activity (17.038 and 18.836 vs. 5.795, measured at [10 mM]). In vivo, polymerized 3D cellular structures were implanted into the distal femoral condyle of 16 New Zealand White Rabbits and were observed for periods from 4 to 12 weeks. New bone formation and bone to implant contact was evaluated by histomorphometry at end of observation. Vinylesters showed similar rates of new bone formation but significantly less (p = 0.002) bone to implant contact, when compared to acrylates. In contrast, the implantation of vinylcarbonate based biophotopolymers led to significantly higher rates of newly formed bone (p < 0.001) and bone to implant contact (p < 0.001). Additionally, distinct signs of polymer degradation could be observed in vinylesters and vinylcarbonates by histology. We conclude, that vinylesters and vinylcarbonates are promising new biophotopolymers, that outmatch available poly(lactic acid) and (meth)acrylate based materials. Full article

(This article belongs to the Special Issue Novel Bone Substitute Materials)

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Open AccessArticle

The Modification of a Tetrafunctional Epoxy and Its Curing Reaction

by Mingming Yu, Bin Feng, Wang Xie, Lin Fang, Hong Li, Liqi Liu, Musu Ren, Jinliang Sun, Jiabao Zhang and Hefeng Hu

Materials 2015, 8(6), 3671-3684; https://doi.org/10.3390/ma8063671 - 18 Jun 2015

Cited by 4 | Viewed by 5986

Abstract

Recent experimental results showed that the T_g of cured resin scarcely decreased and the impact strength of resins increased by over 50% when a tetrafunctional epoxy named N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether (TGDDE) was introduced to an appropriate [...] Read more.

Recent experimental results showed that the T_g of cured resin scarcely decreased and the impact strength of resins increased by over 50% when a tetrafunctional epoxy named N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether (TGDDE) was introduced to an appropriate flexible chain from a dimer fatty acid (DFA). In order to understand the reason for this phenomenon, the modification and the chemical structure of the prepolymer together with the curing reaction and the viscoelasticity of the cured resins were studied in detail in the present work. The results indicated that the modification would help the prepolymer improve its molecular mobility. As a result, the resins could be further cured, resulting in the cross-linking density increasing. This is because the curing efficiency was increased, but the tetrafunctional epoxy was not cured completely due to its large steric hindrance. Moreover, the flexibility of some parts of the networks was improved, which was beneficial for the toughness of the cured resins. Therefore, the toughness of the tetrafunctional resin was improved with little influence on the thermal properties when the epoxies were modified with an appropriate content of DFA. Full article

(This article belongs to the Special Issue Selected Papers from ICETI2014)

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Open AccessArticle

Plasmonic Light Trapping in Thin-Film Solar Cells: Impact of Modeling on Performance Prediction

by Alberto Micco, Marco Pisco, Armando Ricciardi, Lucia V. Mercaldo, Iurie Usatii, Vera La Ferrara, Paola Delli Veneri, Antonello Cutolo and Andrea Cusano

Materials 2015, 8(6), 3648-3670; https://doi.org/10.3390/ma8063648 - 18 Jun 2015

Cited by 5 | Viewed by 5517

Abstract

We present a comparative study on numerical models used to predict the absorption enhancement in thin-film solar cells due to the presence of structured back-reflectors exciting, at specific wavelengths, hybrid plasmonic-photonic resonances. To evaluate the effectiveness of the analyzed models, they have been [...] Read more.

We present a comparative study on numerical models used to predict the absorption enhancement in thin-film solar cells due to the presence of structured back-reflectors exciting, at specific wavelengths, hybrid plasmonic-photonic resonances. To evaluate the effectiveness of the analyzed models, they have been applied in a case study: starting from a U-shaped textured glass thin-film, µc-Si:H solar cells have been successfully fabricated. The fabricated cells, with different intrinsic layer thicknesses, have been morphologically, optically and electrically characterized. The experimental results have been successively compared with the numerical predictions. We have found that, in contrast to basic models based on the underlying schematics of the cell, numerical models taking into account the real morphology of the fabricated device, are able to effectively predict the cells performances in terms of both optical absorption and short-circuit current values. Full article

(This article belongs to the Special Issue Plasmonic Materials)

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813 KiB

Open AccessArticle

Photocatalytic Membrane Reactor for the Removal of C.I. Disperse Red 73

by Valentina Buscio, Stephan Brosillon, Julie Mendret, Martí Crespi and Carmen Gutiérrez-Bouzán

Materials 2015, 8(6), 3633-3647; https://doi.org/10.3390/ma8063633 - 18 Jun 2015

Cited by 42 | Viewed by 6942

Abstract

After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal [...] Read more.

After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal of C.I. Disperse Red 73 from synthetic textile effluents. The titanium dioxide (TiO₂) Aeroxide P25 was selected as photocatalyst. The photocatalytic treatment achieved between 60% and 90% of dye degradation and up to 98% chemical oxygen demand (COD) removal. The influence of different parameters on photocatalytic degradation was studied: pH, initial photocatalyst loading, and dye concentration. The best conditions for dye degradation were pH 4, an initial dye concentration of 50 mg·L⁻¹, and a TiO₂ loading of 2 g·L⁻¹. The photocatalytic membrane treatment provided a high quality permeate, which can be reused. Full article

(This article belongs to the Special Issue Developments in Organic Dyes and Pigments)

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Open AccessArticle

Adsorption, Thermodynamic and Quantum Chemical Studies of 1-hexyl-3-methylimidazolium Based Ionic Liquids as Corrosion Inhibitors for Mild Steel in HCl

by Motsie E. Mashuga, Lukman O. Olasunkanmi, Abolanle S. Adekunle, Sasikumar Yesudass, Mwadham M. Kabanda and Eno E. Ebenso

Materials 2015, 8(6), 3607-3632; https://doi.org/10.3390/ma8063607 - 17 Jun 2015

Cited by 89 | Viewed by 7601

Abstract

The inhibition of mild steel corrosion in 1 M HCl solution by some ionic liquids (ILs) namely, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate [HMIM][TfO], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF₄], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], and 1-hexyl-3-methylimidazolium iodide [HMIM][I] was investigated using electrochemical measurements, spectroscopic analyses and quantum [...] Read more.

The inhibition of mild steel corrosion in 1 M HCl solution by some ionic liquids (ILs) namely, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate [HMIM][TfO], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF₄], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], and 1-hexyl-3-methylimidazolium iodide [HMIM][I] was investigated using electrochemical measurements, spectroscopic analyses and quantum chemical calculations. All the ILs showed appreciably high inhibition efficiency. At 303 K, the results of electrochemical measurements indicated that the studied ILs are mixed-type inhibitors. The adsorption studies showed that all the four ILs adsorb spontaneously on steel surface with [HMIM][TfO], [HMIM][BF₄] and [HMIM][I] obeying Langmuir adsorption isotherm, while [HMIM][PF₆] conformed better with Temkin adsorption isotherm. Spectroscopic analyses suggested the formation of Fe/ILs complexes. Some quantum chemical parameters were calculated to corroborate experimental results. Full article

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4032 KiB

Open AccessArticle

Biomimetic Coating on Porous Alumina for Tissue Engineering: Characterisation by Cell Culture and Confocal Microscopy

by Elizabeth Kolos and Andrew J Ruys

Materials 2015, 8(6), 3584-3606; https://doi.org/10.3390/ma8063584 - 17 Jun 2015

Cited by 10 | Viewed by 7014

Abstract

In this study porous alumina samples were prepared and then coated using the biomimetic coating technique using a five times Simulated Body Fluid (5.0SBF) as the growth solution. A coating was achieved after pre-treatment with concentrated acid. From elemental analysis, the coating contained [...] Read more.

In this study porous alumina samples were prepared and then coated using the biomimetic coating technique using a five times Simulated Body Fluid (5.0SBF) as the growth solution. A coating was achieved after pre-treatment with concentrated acid. From elemental analysis, the coating contained calcium and phosphorous, but also sodium and chlorine. Halite was identified by XRD, a sodium chloride phase. Sintering was done to remove the halite phase. Once halite was burnt off, the calcium phosphate crystals were not covered with halite and, therefore, the apatite phases can be clearly observed. Cell culturing showed sufficient cell attachment to the less porous alumina, Sample B, that has more calcium phosphate growth, while the porous alumina, Sample A, with minimal calcium phosphate growth attained very little cell attachment. This is likely due to the contribution that calcium phosphate plays in the attachment of bone-like cells to a bioinert ceramic such as alumina. These results were repeated on both SEM and confocal microscopy analysis. Confocal microscopy was a novel characterisation approach which gave useful information and was a visual aid. Full article

(This article belongs to the Special Issue Bioceramics)

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661 KiB

Open AccessArticle

A New Predictive Model of Centerline Segregation in Continuous Cast Steel Slabs by Using Multivariate Adaptive Regression Splines Approach

by Paulino José García Nieto, Victor Manuel González Suárez, Juan Carlos Álvarez Antón, Ricardo Mayo Bayón, José Ángel Sirgo Blanco and Ana María Díaz Fernández

Materials 2015, 8(6), 3562-3583; https://doi.org/10.3390/ma8063562 - 17 Jun 2015

Cited by 15 | Viewed by 9561

Abstract

The aim of this study was to obtain a predictive model able to perform an early detection of central segregation severity in continuous cast steel slabs. Segregation in steel cast products is an internal defect that can be very harmful when slabs are [...] Read more.

The aim of this study was to obtain a predictive model able to perform an early detection of central segregation severity in continuous cast steel slabs. Segregation in steel cast products is an internal defect that can be very harmful when slabs are rolled in heavy plate mills. In this research work, the central segregation was studied with success using the data mining methodology based on multivariate adaptive regression splines (MARS) technique. For this purpose, the most important physical-chemical parameters are considered. The results of the present study are two-fold. In the first place, the significance of each physical-chemical variable on the segregation is presented through the model. Second, a model for forecasting segregation is obtained. Regression with optimal hyperparameters was performed and coefficients of determination equal to 0.93 for continuity factor estimation and 0.95 for average width were obtained when the MARS technique was applied to the experimental dataset, respectively. The agreement between experimental data and the model confirmed the good performance of the latter. Full article

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2259 KiB

Open AccessArticle

Preparation of Advanced Carbon Anode Materials from Mesocarbon Microbeads for Use in High C-Rate Lithium Ion Batteries

by Ming-Dar Fang, Tsung-Han Ho, Jui-Pin Yen, Yu-Run Lin, Jin-Long Hong, She-Huang Wu and Jiin-Jiang Jow

Materials 2015, 8(6), 3550-3561; https://doi.org/10.3390/ma8063550 - 17 Jun 2015

Cited by 37 | Viewed by 8505

Abstract

Mesophase soft carbon (MSC) and mesophase graphite (SMG), for use in comparative studies of high C-rate Lithium Ion Battery (LIB) anodes, were made by heating mesocarbon microbeads (MCMB) at 1300 °C and 3000 °C; respectively. The crystalline structures and morphologies of the MSC, [...] Read more.

Mesophase soft carbon (MSC) and mesophase graphite (SMG), for use in comparative studies of high C-rate Lithium Ion Battery (LIB) anodes, were made by heating mesocarbon microbeads (MCMB) at 1300 °C and 3000 °C; respectively. The crystalline structures and morphologies of the MSC, SMG, and commercial hard carbon (HC) were investigated by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. Additionally, their electrochemical properties, when used as anode materials in LIBs, were also investigated. The results show that MSC has a superior charging rate capability compared to SMG and HC. This is attributed to MSC having a more extensive interlayer spacing than SMG, and a greater number of favorably-oriented pathways when compared to HC. Full article

(This article belongs to the Special Issue Selected Papers from ICETI2014)

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465 KiB

Open AccessReview

The Use of Quaternary Ammonium to Combat Dental Caries

by Yang Ge, Suping Wang, Xuedong Zhou, Haohao Wang, Hockin H. K. Xu and Lei Cheng

Materials 2015, 8(6), 3532-3549; https://doi.org/10.3390/ma8063532 - 17 Jun 2015

Cited by 51 | Viewed by 8322

Abstract

Resin composites and adhesives are increasingly popular in dental restorations, but secondary caries is one of the main reasons for restoration failure. Quaternary ammonium monomers (QAMs) have an anti-microbial effect and are widely used in many fields. Since the concept of the immobilized [...] Read more.

Resin composites and adhesives are increasingly popular in dental restorations, but secondary caries is one of the main reasons for restoration failure. Quaternary ammonium monomers (QAMs) have an anti-microbial effect and are widely used in many fields. Since the concept of the immobilized antibacterial effect was put forward, dental restorations containing QAMs have been studied to reduce secondary caries. Previous studies have been struggling to develop novel anti-caries materials which might have triple benefits: good mechanical properties, antibacterial effects and remineralization potentials. Different kinds of QAMs have been proven to be effective in inhibiting the growth and metabolism of biofilms. Combination of QAMs and other nanoparticles in resin composites and adhesives could enhance their anti-caries capability. Therefore, QAMs are promising to show significant impact on the future of restorative and preventive dentistry. Full article

(This article belongs to the Special Issue Dental Materials)

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Open AccessArticle

Role of Interphase in the Mechanical Behavior of Silica/Epoxy Resin Nanocomposites

by Yi Hua, Linxia Gu, Sundaralingam Premaraj and Xiaodong Zhang

Materials 2015, 8(6), 3519-3531; https://doi.org/10.3390/ma8063519 - 16 Jun 2015

Cited by 30 | Viewed by 5876

Abstract

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had [...] Read more.

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had significant influence on the effective stiffness of nanocomposites, while its sensitivities with respect to both the thickness and the gradient property of the interphase was minimal. The stiffer interphase demonstrated a higher load-sharing capacity, which also increased the stress distribution uniformity within the resin nanocomposites. Under the condition of imperfect interfacial bonding, the effective stiffness of nanocomposites was much lower, which was in good agreement with the documented experimental observations. This work could shed some light on the design and manufacturing of resin nanocomposites. Full article

(This article belongs to the Special Issue Dental Materials)

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Open AccessArticle

Highly Stretchable, Biocompatible, Striated Substrate Made from Fugitive Glue

by Wei Li, Tomas Lucioni, Xinyi Guo, Amanda Smelser and Martin Guthold

Materials 2015, 8(6), 3508-3518; https://doi.org/10.3390/ma8063508 - 15 Jun 2015

Cited by 3 | Viewed by 5698

Abstract

We developed a novel substrate made from fugitive glue (styrenic block copolymer) that can be used to analyze the effects of large strains on biological samples. The substrate has the following attributes: (1) It is easy to make from inexpensive components; (2) It [...] Read more.

We developed a novel substrate made from fugitive glue (styrenic block copolymer) that can be used to analyze the effects of large strains on biological samples. The substrate has the following attributes: (1) It is easy to make from inexpensive components; (2) It is transparent and can be used in optical microscopy; (3) It is extremely stretchable as it can be stretched up to 700% strain; (4) It can be micro-molded, for example we created micro-ridges that are 6 μm high and 13 μm wide; (5) It is adhesive to biological fibers (we tested fibrin fibers), and can be used to uniformly stretch those fibers; (6) It is non-toxic to cells (we tested human mammary epithelial cells); (7) It can tolerate various salt concentrations up to 5 M NaCl and low (pH 0) and high (pH 14) pH values. Stretching of this extraordinary stretchable substrate is relatively uniform and thus, can be used to test multiple cells or fibers in parallel under the same conditions. Full article

(This article belongs to the Special Issue Mechanics of Biomaterials)

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Open AccessArticle

Catalytically Enhanced Hydrogen Sorption in Mg-MgH₂ by Coupling Vanadium-Based Catalyst and Carbon Nanotubes

by Atikah Kadri, Yi Jia, Zhigang Chen and Xiangdong Yao

Materials 2015, 8(6), 3491-3507; https://doi.org/10.3390/ma8063491 - 12 Jun 2015

Cited by 22 | Viewed by 6357

Abstract

Mg (MgH₂)-based composites, using carbon nanotubes (CNTs) and pre-synthesized vanadium-based complex (VCat) as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH₂ was observed for an ultra-fast absorption rate of [...] Read more.

Mg (MgH₂)-based composites, using carbon nanotubes (CNTs) and pre-synthesized vanadium-based complex (VCat) as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH₂ was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD) results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H₂ and 11 J/mol H₂·K, respectively, as compared to those of the commercial MgH₂, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time) are better to enhance the hydrogen sorption performance. Full article

(This article belongs to the Special Issue Hydrogen Storage Materials)

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Open AccessArticle

Mechanical and Thermal Dehydrogenation of the Mechano-Chemically Synthesized Calcium Alanate (Ca(AlH₄)₂) and Lithium Chloride (LiCl) Composite

by Robert A. Varin, Ewelina E. Kościuczyk and Tomasz Czujko

Materials 2015, 8(6), 3479-3490; https://doi.org/10.3390/ma8063479 - 12 Jun 2015

Cited by 2 | Viewed by 5213

Abstract

LiAlH₄ and CaCl₂ were employed for mechano-chemical activation synthesis (MCAS) of Ca(AlH₄)₂ and LiCl hydride composite. After short ball milling time, their X-ray diffraction (XRD) peaks are clearly observed. After ball milling for a longer duration than 0.5 [...] Read more.

LiAlH₄ and CaCl₂ were employed for mechano-chemical activation synthesis (MCAS) of Ca(AlH₄)₂ and LiCl hydride composite. After short ball milling time, their X-ray diffraction (XRD) peaks are clearly observed. After ball milling for a longer duration than 0.5 h, the CaAlH₅ diffraction peaks are observed which indicates that Ca(AlH₄)₂ starts decomposing during ball milling into CaAlH₅+Al+1.5H₂. It is estimated that less than 1 wt % H₂ was mechanically dehydrogenated in association with decomposition reaction. After 2.5 h of ball milling, no Ca(AlH₄)₂ diffraction peaks were observed on XRD patterns which suggests that Ca(AlH₄)₂ was decomposed. Thermal behavior of ball milled powders, which was investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicates that a certain fraction of Ca(AlH₄)₂ could have been disordered/amorphized during ball milling being undetectable by XRD. The apparent activation energy for the decomposition of Ca(AlH₄)₂ and CaAlH₅ equals 135 kJ/mol and 183 kJ/mol, respectively. Full article

(This article belongs to the Special Issue Hydrogen Storage Materials)

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4003 KiB

Open AccessArticle

Effect of Boron Doping on Cellular Discontinuous Precipitation for Age-Hardenable Cu–Ti Alloys

by Satoshi Semboshi, Jun Ikeda, Akihiro Iwase, Takayuki Takasugi and Shigeru Suzuki

Materials 2015, 8(6), 3467-3478; https://doi.org/10.3390/ma8063467 - 11 Jun 2015

Cited by 24 | Viewed by 5980

Abstract

The effects of boron doping on the microstructural evolution and mechanical and electrical properties of age-hardenable Cu–4Ti (at.%) alloys are investigated. In the quenched Cu–4Ti–0.03B (at.%) alloy, elemental B (boron) is preferentially segregated at the grain boundaries of the supersaturated solid-solution phase. The [...] Read more.

The effects of boron doping on the microstructural evolution and mechanical and electrical properties of age-hardenable Cu–4Ti (at.%) alloys are investigated. In the quenched Cu–4Ti–0.03B (at.%) alloy, elemental B (boron) is preferentially segregated at the grain boundaries of the supersaturated solid-solution phase. The aging behavior of the B-doped alloy is mostly similar to that of conventional age-hardenable Cu–Ti alloys. In the early stage of aging at 450 °C, metastable β′-Cu₄Ti with fine needle-shaped precipitates continuously form in the matrix phase. Cellular discontinuous precipitates composed of the stable β-Cu₄Ti and solid-solution laminates are then formed and grown at the grain boundaries. However, the volume fraction of the discontinuous precipitates is lower in the Cu–4Ti–0.03B alloy than the Cu–4Ti alloy, particularly in the over-aging period of 72–120 h. The suppression of the formation of discontinuous precipitates eventually results in improvement of the hardness and tensile strength. It should be noted that minor B doping of Cu–Ti alloys also effectively enhances the elongation to fracture, which should be attributed to segregation of B at the grain boundaries. Full article

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

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1560 KiB

Open AccessArticle

The Concept about the Regeneration of Spent Borohydrides and Used Catalysts from Green Electricity

by Cheng-Hong Liu and Bing-Hung Chen

Materials 2015, 8(6), 3456-3466; https://doi.org/10.3390/ma8063456 - 10 Jun 2015

Cited by 12 | Viewed by 6467

Abstract

Currently, the Brown-Schlesinger process is still regarded as the most common and mature method for the commercial production of sodium borohydride (NaBH₄). However, the metallic sodium, currently produced from the electrolysis of molten NaCl that is mass-produced by evaporation of seawater [...] Read more.

Currently, the Brown-Schlesinger process is still regarded as the most common and mature method for the commercial production of sodium borohydride (NaBH₄). However, the metallic sodium, currently produced from the electrolysis of molten NaCl that is mass-produced by evaporation of seawater or brine, is probably the most costly raw material. Recently, several reports have demonstrated the feasibility of utilizing green electricity such as offshore wind power to produce metallic sodium through electrolysis of seawater. Based on this concept, we have made improvements and modified our previously proposed life cycle of sodium borohydride (NaBH₄) and ammonia borane (NH₃BH₃), in order to further reduce costs in the conventional Brown-Schlesinger process. In summary, the revision in the concept combining the regeneration of the spent borohydrides and the used catalysts with the green electricity is reflected in (1) that metallic sodium could be produced from NaCl of high purity obtained from the conversion of the byproduct in the synthesis of NH₃BH₃ to devoid the complicated purification procedures if produced from seawater; and (2) that the recycling and the regeneration processes of the spent NaBH₄ and NH₃BH₃ as well as the used catalysts could be simultaneously carried out and combined with the proposed life cycle of borohydrides. Full article

(This article belongs to the Special Issue Hydrogen Storage Materials)

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2014 KiB

Open AccessArticle

Ru-N-C Hybrid Nanocomposite for Ammonia Dehydrogenation: Influence of N-doping on Catalytic Activity

by Nguyen Thi Bich Hien, Hyo Young Kim, Mina Jeon, Jin Hee Lee, Muhammad Ridwan, Rizcky Tamarany and Chang Won Yoon

Materials 2015, 8(6), 3442-3455; https://doi.org/10.3390/ma8063442 - 10 Jun 2015

Cited by 19 | Viewed by 7892

Abstract

For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl₃·6H₂O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the [...] Read more.

For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl₃·6H₂O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH₃ conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity. Full article

(This article belongs to the Special Issue Hydrogen Storage Materials)

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6540 KiB

Open AccessArticle

Directional Solidification Microstructure of a Ni-Based Superalloy: Influence of a Weak Transverse Magnetic Field

by Xu Li, Jun Wang, Jiao Zhang, Yanfeng Han and Xi Li

Materials 2015, 8(6), 3428-3441; https://doi.org/10.3390/ma8063428 - 10 Jun 2015

Cited by 7 | Viewed by 8582

Abstract

A Ni-based superalloy CMSX-6 was directionally solidified at various drawing speeds (5–20 μm·s⁻¹) and diameters (4 mm, 12 mm) under a 0.5 T weak transverse magnetic field. The results show that the application of a weak transverse magnetic field significantly modified [...] Read more.

A Ni-based superalloy CMSX-6 was directionally solidified at various drawing speeds (5–20 μm·s⁻¹) and diameters (4 mm, 12 mm) under a 0.5 T weak transverse magnetic field. The results show that the application of a weak transverse magnetic field significantly modified the solidification microstructure. It was found that if the drawing speed was lower than 10 μm·s⁻¹, the magnetic field caused extensive macro-segregation in the mushy zone, and a change in the mushy zone length. The magnetic field significantly decreases the size of γ’ and the content of γ-γ’ eutectic. The formation of macro-segregation under a weak magnetic field was attributed to the interdendritic solute transport driven by the thermoelectric magnetic convection (TEMC). The γ’ phase refinement could be attributed to a decrease in nucleation activation energy owing to the magnetic field during solid phase transformation. The change of element segregation is responsible for the content decrease of γ-γ’ eutectic. Full article

(This article belongs to the Section Advanced Materials Characterization)

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4037 KiB

Open AccessReview

Nanocomposites Based on Thermoplastic Polymers and Functional Nanofiller for Sensor Applications

by Serena Coiai, Elisa Passaglia, Andrea Pucci and Giacomo Ruggeri

Materials 2015, 8(6), 3377-3427; https://doi.org/10.3390/ma8063377 - 10 Jun 2015

Cited by 65 | Viewed by 11097

Abstract

Thermoplastic polymers like polyolefins, polyesters, polyamide, and styrene polymers are the most representative commodity plastics thanks to their cost-efficient manufacturing processes, excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide [...] Read more.

Thermoplastic polymers like polyolefins, polyesters, polyamide, and styrene polymers are the most representative commodity plastics thanks to their cost-efficient manufacturing processes, excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of such materials by conferring on them new properties through mixing and blending with different additives. In this latter context, nanocomposites have recently offered new exciting possibilities. This review discusses the successful use of nanostructured dispersed substrates in designing new stimuli-responsive nanocomposites; in particular, it provides an updated description of the synthetic routes to prepare nanostructured systems having the typical properties of thermoplastic polymers (continuous matrix), but showing enhanced optical, conductive, and thermal features dependent on the dispersion topology. The controlled nanodispersion of functional labeled clays, noble metal nanoparticles and carbon nanotubes is here evidenced to play a key role in producing hybrid thermoplastic materials that have been used in the design of devices, such as NLO devices, chemiresistors, temperature and deformation sensors. Full article

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3989 KiB

Open AccessArticle

Numerical Study on Crack Propagation in Brittle Jointed Rock Mass Influenced by Fracture Water Pressure

by Yong Li, Hao Zhou, Weishen Zhu, Shucai Li and Jian Liu

Materials 2015, 8(6), 3364-3376; https://doi.org/10.3390/ma8063364 - 09 Jun 2015

Cited by 56 | Viewed by 6573

Abstract

The initiation, propagation, coalescence and failure mode of brittle jointed rock mass influenced by fissure water pressure have always been studied as a hot issue in the society of rock mechanics and engineering. In order to analyze the damage evolution process of jointed [...] Read more.

The initiation, propagation, coalescence and failure mode of brittle jointed rock mass influenced by fissure water pressure have always been studied as a hot issue in the society of rock mechanics and engineering. In order to analyze the damage evolution process of jointed rock mass under fracture water pressure, a novel numerical model on the basis of secondary development in fast Lagrangian analysis of continua (FLAC3D) is proposed to simulate the fracture development of jointed rock mass under fracture water pressure. To validate the feasibility of this numerical model, the failure process of a numerical specimen under uniaxial compression containing pre-existing fissures is simulated and compared with the results obtained from the lab experiments, and they are found to be in good agreement. Meanwhile, the propagation of cracks, variations of stress and strain, peak strength and crack initiation principles are further analyzed. It is concluded that the fissure water has a significant reducing effect on the strength and stability of the jointed rock mass. Full article

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1150 KiB

Open AccessArticle

The pH Sensing Properties of RF Sputtered RuO₂ Thin-Film Prepared Using Different Ar/O₂ Flow Ratio

by Ali Sardarinejad, Devendra Kumar Maurya and Kamal Alameh

Materials 2015, 8(6), 3352-3363; https://doi.org/10.3390/ma8063352 - 09 Jun 2015

Cited by 39 | Viewed by 6288

Abstract

The influence of the Ar/O₂ gas ratio during radio frequency (RF) sputtering of the RuO₂ sensing electrode on the pH sensing performance is investigated. The developed pH sensor consists in an RF sputtered ruthenium oxide thin-film sensing electrode, in conjunction with [...] Read more.

The influence of the Ar/O₂ gas ratio during radio frequency (RF) sputtering of the RuO₂ sensing electrode on the pH sensing performance is investigated. The developed pH sensor consists in an RF sputtered ruthenium oxide thin-film sensing electrode, in conjunction with an electroplated Ag/AgCl reference electrode. The performance and characterization of the developed pH sensors in terms of sensitivity, response time, stability, reversibility, and hysteresis are investigated. Experimental results show that the pH sensor exhibits super-Nernstian slopes in the range of 64.33–73.83 mV/pH for Ar/O₂ gas ratio between 10/0–7/3. In particular, the best pH sensing performance, in terms of sensitivity, response time, reversibility and hysteresis, is achieved when the Ar/O₂ gas ratio is 8/2, at which a high sensitivity, a low hysteresis and a short response time are attained simultaneously. Full article

(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)

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836 KiB

Open AccessArticle

Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

by Sergio Diez-Berart, David O. López, Josep Salud, José Antonio Diego, Jordi Sellarès, Beatriz Robles-Hernández, María Rosario De la Fuente and María Blanca Ros

Materials 2015, 8(6), 3334-3351; https://doi.org/10.3390/ma8063334 - 08 Jun 2015

Cited by 9 | Viewed by 4600

Abstract

In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to [...] Read more.

In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations. Full article

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3713 KiB

Open AccessArticle

Tension-Tension Fatigue Behavior of Unidirectional C/Sic Ceramic-Matrix Composite at Room Temperature and 800 °C in Air Atmosphere

by Longbiao Li

Materials 2015, 8(6), 3316-3333; https://doi.org/10.3390/ma8063316 - 08 Jun 2015

Cited by 19 | Viewed by 5695

Abstract

The tension-tension fatigue behavior of unidirectional C/SiC ceramic-matrix composite at room temperature and 800 °C under air has been investigated. The fatigue hysteresis modulus and fatigue hysteresis loss energy corresponding to different number of applied cycles have been analyzed. The fatigue hysteresis loops [...] Read more.

The tension-tension fatigue behavior of unidirectional C/SiC ceramic-matrix composite at room temperature and 800 °C under air has been investigated. The fatigue hysteresis modulus and fatigue hysteresis loss energy corresponding to different number of applied cycles have been analyzed. The fatigue hysteresis loops models for different interface slip cases have been derived based on the fatigue damage mechanism of fiber slipping relative to matrix in the interface debonded region upon unloading and subsequent reloading. The fiber/matrix interface shear stress has been estimated for different numbers of applied cycles. By combining the interface shear stress degradation model and fibers strength degradation model with fibers failure model, the tension-tension fatigue life S-N curves of unidirectional C/SiC composite at room temperature and 800 °C under air have been predicted. Full article

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334 KiB

Open AccessArticle

Comparative Shear-Bond Strength of Six Dental Self-Adhesive Resin Cements to Zirconia

by Si-Eun Lee, Ji-Hyeon Bae, Jae-Won Choi, Yong-Chan Jeon, Chang-Mo Jeong, Mi-Jung Yoon and Jung-Bo Huh

Materials 2015, 8(6), 3306-3315; https://doi.org/10.3390/ma8063306 - 05 Jun 2015

Cited by 21 | Viewed by 6391

Abstract

This study compared shear bond strength (SBS) of six self-adhesive resin cements (SARC) and one resin-modified glass ionomer cement (RMGIC) to zirconia before and after thermocycling. The cylinder shape (Φ 2.35 mm × 3 mm) of six SARCs (G-CEM LinkAce (GLA), Maxcem Elite [...] Read more.

This study compared shear bond strength (SBS) of six self-adhesive resin cements (SARC) and one resin-modified glass ionomer cement (RMGIC) to zirconia before and after thermocycling. The cylinder shape (Φ 2.35 mm × 3 mm) of six SARCs (G-CEM LinkAce (GLA), Maxcem Elite (MAX), Clearfil SA Luting (CSL), PermaCem 2.0 (PM2), Rely-X U200 (RXU), Smartcem 2 (SC2)) were bonded to the top surface of the zirconia specimens with light-curing. RMGIC (Fujicem (FJC)) was bonded to the specimens with self-curing. The shear bond strength of all cemented specimens was measured with universal testing machine. Half of the specimens were thermocycled 5000 times before shear bonding strength testing. Fractured surfaces were examined with a field-emission SEM (10,000×) and analyzed by energy dispersive x-ray analysis. MAX, PM2, SC2 group without thermocycling and GLA, MAX, PM2 group with thermocycling showed adhesive failure, but GLA, CSL, RXU, FJC group without thermocycling and SLC, RXU, SC2, FJC group with thermocycling indicated cohesive failure. Within the limitation of this study, All of SARCs except MAX demonstrated higher bond strength than that of RMGIC regardless of thermocycling. Also, SARC containing MDP monomers (CSL) retained better bonds than other cements. Full article

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Materials, Volume 8, Issue 6 (June 2015) – 54 articles , Pages 2849-3792

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