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Materials, Volume 7, Issue 6 (June 2014), Pages 4088-4877

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Open AccessArticle An Optimal Cure Process to Minimize Residual Void and Optical Birefringence for a LED Silicone Encapsulant
Materials 2014, 7(6), 4088-4104; doi:10.3390/ma7064088
Received: 21 March 2014 / Revised: 8 May 2014 / Accepted: 19 May 2014 / Published: 27 May 2014
Cited by 2 | PDF Full-text (17122 KB) | HTML Full-text | XML Full-text
Abstract
Silicone resin has recently attracted great attention as a high-power Light Emitting Diode (LED) encapsulant material due to its good thermal stability and optical properties. In general, the abrupt curing reaction of the silicone resin for the LED encapsulant during the curing process
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Silicone resin has recently attracted great attention as a high-power Light Emitting Diode (LED) encapsulant material due to its good thermal stability and optical properties. In general, the abrupt curing reaction of the silicone resin for the LED encapsulant during the curing process induces reduction in the mechanical and optical properties of the LED product due to the generation of residual void and moisture, birefringence, and residual stress in the final formation. In order to prevent such an abrupt curing reaction, the reduction of residual void and birefringence of the silicone resin was observed through experimentation by introducing the multi-step cure processes, while the residual stress was calculated by conducting finite element analysis that coupled the heat of cure reaction and cure shrinkage. The results of experiment and analysis showed that it was during the three-step curing process that the residual void, birefringence, and residual stress reduced the most in similar tendency. Through such experimentation and finite element analysis, the study was able to confirm that the optimization of the LED encapsulant packaging process was possible. Full article
Open AccessArticle Biocompatibility and Surface Properties of TiO2 Thin Films Deposited by DC Magnetron Sputtering
Materials 2014, 7(6), 4105-4117; doi:10.3390/ma7064105
Received: 10 April 2014 / Revised: 1 May 2014 / Accepted: 5 May 2014 / Published: 27 May 2014
Cited by 11 | PDF Full-text (4841 KB) | HTML Full-text | XML Full-text
Abstract
We present the study of the biocompatibility and surface properties of titanium dioxide (TiO2) thin films deposited by direct current magnetron sputtering. These films are deposited on a quartz substrate at room temperature and annealed with different temperatures (100, 300, 500,
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We present the study of the biocompatibility and surface properties of titanium dioxide (TiO2) thin films deposited by direct current magnetron sputtering. These films are deposited on a quartz substrate at room temperature and annealed with different temperatures (100, 300, 500, 800 and 1100 °C). The biocompatibility of the TiO2 thin films is analyzed using primary cultures of dorsal root ganglion (DRG) of Wistar rats, whose neurons are incubated on the TiO2 thin films and on a control substrate during 18 to 24 h. These neurons are activated by electrical stimuli and its ionic currents and action potential activity recorded. Through X-ray diffraction (XRD), the surface of TiO2 thin films showed a good quality, homogeneity and roughness. The XRD results showed the anatase to rutile phase transition in TiO2 thin films at temperatures between 500 and 1100 °C. This phase had a grain size from 15 to 38 nm, which allowed a suitable structural and crystal phase stability of the TiO2 thin films for low and high temperature. The biocompatibility experiments of these films indicated that they were appropriated for culture of living neurons which displayed normal electrical behavior. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Research on the Micro Sheet Stamping Process Using Plasticine as Soft Punch
Materials 2014, 7(6), 4118-4131; doi:10.3390/ma7064118
Received: 17 December 2013 / Revised: 8 April 2014 / Accepted: 21 May 2014 / Published: 27 May 2014
Cited by 2 | PDF Full-text (8728 KB) | HTML Full-text | XML Full-text
Abstract
Plasticine is widely used in the analysis of metal forming processes, due to its excellent material flow ability. In this study, plasticine is used as the soft punch to fabricate array micro-channels on metal sheet in the micro sheet stamping process. This is
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Plasticine is widely used in the analysis of metal forming processes, due to its excellent material flow ability. In this study, plasticine is used as the soft punch to fabricate array micro-channels on metal sheet in the micro sheet stamping process. This is because plasticine can produce a large material flow after being subjected to force and through the material flow, the plasticine can cause the sheet to fill into the micro-channels of the rigid die, leading to the generation of micro-channels in the sheet. The distribution of array micro-channels was investigated as well as the influence of load forces on the sheet deformations. It was found that the depth of micro-channels increases as the load force increases. When the load force reaches a certain level, a crack can be observed. The micro sheet stamping process was also investigated by the method of numerical simulation. The obtained experimental and numerical results for the stamping process showed that they were in good agreement. Additionally, from the simulation results, it can be seen that the corner region of the micro-channel-shape work piece has a risk to crack due to the existence of maximum von Mises stress and significant thinning. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
Open AccessArticle New Lyotropic Mixtures with Non-Chiral N-Acylamino Acid Surfactants Presenting the Biaxial Nematic Phase Investigated by Laser Conoscopy, Polarized Optical Microscopy and X-ray Diffraction
Materials 2014, 7(6), 4132-4147; doi:10.3390/ma7064132
Received: 8 March 2014 / Revised: 22 April 2014 / Accepted: 21 May 2014 / Published: 27 May 2014
Cited by 2 | PDF Full-text (1104 KB) | HTML Full-text | XML Full-text
Abstract
Amino acid-based surfactants were used as the main surfactants to prepare new lyotropic mixtures presenting three nematic phases. One of them is biaxial (NB), and the two others are uniaxial, discotic (ND) and calamitic (NC
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Amino acid-based surfactants were used as the main surfactants to prepare new lyotropic mixtures presenting three nematic phases. One of them is biaxial (NB), and the two others are uniaxial, discotic (ND) and calamitic (NC). These surfactants were the non-chiral molecules, potassium N-dodecanoyl-DL-alaninate (DL-KDDA), potassium N-dodecanoyl-DL-serinate (DL-KDDS), disodium N-dodecanoyl-DL-aspartate (DL-NaDDAs) and potassium N-dodecanoyl-glycinate (KDDGly). Measurements of the optical birefringences and X-ray diffraction analysis were used to characterize the nematic phases and phase transitions. Mixtures with DL-KDDS exhibited the largest biaxial phase domain (~9 °C) with respect to the other mixtures in this study. The results obtained with the KDDGly mixture showed that the existence of hydrogen bonding between the head groups of the surfactant molecules seems to hinder the orientation of the micelles under the action of an external magnetic field. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessArticle Hybrid Composites Based on Carbon Fiber/Carbon Nanofilament Reinforcement
Materials 2014, 7(6), 4182-4195; doi:10.3390/ma7064182
Received: 7 March 2014 / Revised: 2 May 2014 / Accepted: 23 May 2014 / Published: 28 May 2014
Cited by 7 | PDF Full-text (1853 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanofilament and nanotubes (CNTs) have shown promise for enhancing the mechanical properties of fiber-reinforced composites (FRPs) and imparting multi-functionalities to them. While direct mixing of carbon nanofilaments with the polymer matrix in FRPs has several drawbacks, a high volume of uniform nanofilaments
[...] Read more.
Carbon nanofilament and nanotubes (CNTs) have shown promise for enhancing the mechanical properties of fiber-reinforced composites (FRPs) and imparting multi-functionalities to them. While direct mixing of carbon nanofilaments with the polymer matrix in FRPs has several drawbacks, a high volume of uniform nanofilaments can be directly grown on fiber surfaces prior to composite fabrication. This study demonstrates the ability to create carbon nanofilaments on the surface of carbon fibers employing a synthesis method, graphitic structures by design (GSD), in which carbon structures are grown from fuel mixtures using nickel particles as the catalyst. The synthesis technique is proven feasible to grow nanofilament structures—from ethylene mixtures at 550 °C—on commercial polyacrylonitrile (PAN)-based carbon fibers. Raman spectroscopy and electron microscopy were employed to characterize the surface-grown carbon species. For comparison purposes, a catalytic chemical vapor deposition (CCVD) technique was also utilized to grow multiwall CNTs (MWCNTs) on carbon fiber yarns. The mechanical characterization showed that composites using the GSD-grown carbon nanofilaments outperform those using the CCVD-grown CNTs in terms of stiffness and tensile strength. The results suggest that further optimization of the GSD growth time, patterning and thermal shield coating of the carbon fibers is required to fully materialize the potential benefits of the GSD technique. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
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Open AccessArticle Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols
Materials 2014, 7(6), 4196-4223; doi:10.3390/ma7064196
Received: 28 November 2013 / Revised: 28 December 2013 / Accepted: 12 May 2014 / Published: 30 May 2014
Cited by 5 | PDF Full-text (2964 KB) | HTML Full-text | XML Full-text
Abstract
Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2
[...] Read more.
Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF3·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF3·MEA into the clay galleries of nanocomposites containing 2 wt% MMT. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle Effect of Processing Steps on the Mechanical Properties and Surface Appearance of 6063 Aluminium Extruded Products
Materials 2014, 7(6), 4224-4242; doi:10.3390/ma7064224
Received: 28 March 2014 / Revised: 18 May 2014 / Accepted: 19 May 2014 / Published: 30 May 2014
Cited by 5 | PDF Full-text (1062 KB) | HTML Full-text | XML Full-text
Abstract
6063 aluminum anodized extrusions may exhibit a common surface defect known as streaking, characterized by the formation of narrow bands with a surface gloss different from the surrounding material. The origin of this banding lies in the differential surface topography produced after etching
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6063 aluminum anodized extrusions may exhibit a common surface defect known as streaking, characterized by the formation of narrow bands with a surface gloss different from the surrounding material. The origin of this banding lies in the differential surface topography produced after etching during the anodizing stage, shown to be connected to certain microstructural characteristics. The present study has attempted to determine the origin of these defects and measure the mechanical properties in these zones, properties which were either barely acceptable or did not meet the specification’s requirements. Quantitative metallography and mechanical testing, both tensile and microhardness, were used for materials assessment at the different steps of the process of manufacturing 6063 anodized extrusions. The results of this research show that nonequilibrium solidification rates during billet casting could lead to the formation of coarse eutectic Mg2Si particles which have a deleterious effect on both mechanical properties and surface appearance in the anodized condition. However, differences in the size and density of the coarse Mg2Si particles have been found to exist in the streak profile compared to the surrounding zones. The study revealed the importance of these particles in explaining the origin of the marginal or sub-marginal properties and anodizing surface defects found. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
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Open AccessArticle Active Iron Sites of Disordered Mesoporous Silica Catalyst FeKIL-2 in the Oxidation of Volatile Organic Compounds (VOC)
Materials 2014, 7(6), 4243-4257; doi:10.3390/ma7064243
Received: 16 February 2014 / Revised: 21 May 2014 / Accepted: 23 May 2014 / Published: 30 May 2014
Cited by 1 | PDF Full-text (798 KB) | HTML Full-text | XML Full-text
Abstract
Iron-functionalized disordered mesoporous silica (FeKIL-2) is a promising, environmentally friendly, cost-effective and highly efficient catalyst for the elimination of volatile organic compounds (VOCs) from polluted air via catalytic oxidation. In this study, we investigated the type of catalytically active iron sites for different
[...] Read more.
Iron-functionalized disordered mesoporous silica (FeKIL-2) is a promising, environmentally friendly, cost-effective and highly efficient catalyst for the elimination of volatile organic compounds (VOCs) from polluted air via catalytic oxidation. In this study, we investigated the type of catalytically active iron sites for different iron concentrations in FeKIL-2 catalysts using advanced characterization of the local environment of iron atoms by a combination of X-ray Absorption Spectroscopy Techniques (XANES, EXAFS) and Atomic-Resolution Scanning Transmission Electron Microscopy (AR STEM). We found that the molar ratio Fe/Si ≤ 0.01 leads to the formation of stable, mostly isolated Fe3+ sites in the silica matrix, while higher iron content Fe/Si > 0.01 leads to the formation of oligonuclear iron clusters. STEM imaging and EELS techniques confirmed the existence of these clusters. Their size ranges from one to a few nanometers, and they are unevenly distributed throughout the material. The size of the clusters was also found to be similar, regardless of the nominal concentration of iron (Fe/Si = 0.02 and Fe/Si = 0.05). From the results obtained from sample characterization and model catalytic tests, we established that the enhanced activity of FeKIL-2 with the optimal Fe/Si = 0.01 ratio can be attributed to: (1) the optimal concentration of stable isolated Fe3+ in the silica support; and (2) accelerated diffusion of the reactants in disordered mesoporous silica (FeKIL-2) when compared to ordered mesoporous silica materials (FeSBA-15, FeMCM-41). Full article
(This article belongs to the Special Issue Advances in Nanoporous Materials)
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Open AccessArticle Experimental Analysis of the Influence of Drill Point Angle and Wear on the Drilling of Woven CFRPs
Materials 2014, 7(6), 4258-4271; doi:10.3390/ma7064258
Received: 8 March 2014 / Revised: 1 April 2014 / Accepted: 26 May 2014 / Published: 30 May 2014
Cited by 7 | PDF Full-text (2135 KB) | HTML Full-text | XML Full-text
Abstract
This paper focuses on the effect of the drill geometry on the drilling of woven Carbon Fiber Reinforced Polymer composite (CFRPs). Although different geometrical effects can be considered in drilling CFRPs, the present work focuses on the influence of point angle and wear
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This paper focuses on the effect of the drill geometry on the drilling of woven Carbon Fiber Reinforced Polymer composite (CFRPs). Although different geometrical effects can be considered in drilling CFRPs, the present work focuses on the influence of point angle and wear because they are the important factors influencing hole quality and machining forces. Surface quality was evaluated in terms of delamination and superficial defects. Three different point angles were tested representative of the geometries commonly used in the industry. Two wear modes were considered, being representative of the wear patterns commonly observed when drilling CFRPs: flank wear and honed cutting edge. It was found that the crossed influence of the point angle and wear were significant to the thrust force. Delamination at the hole entry and exit showed opposite trends with the change of geometry. Also, cutting parameters were checked showing the feed’s dominant influence on surface damage. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
Open AccessArticle Janus Nematic Colloids with Designable Valence
Materials 2014, 7(6), 4272-4281; doi:10.3390/ma7064272
Received: 3 April 2014 / Revised: 21 May 2014 / Accepted: 23 May 2014 / Published: 30 May 2014
Cited by 5 | PDF Full-text (1136 KB) | HTML Full-text | XML Full-text
Abstract
Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show
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Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessArticle Permeation Properties and Pore Structure of Surface Layer of Fly Ash Concrete
Materials 2014, 7(6), 4282-4296; doi:10.3390/ma7064282
Received: 15 April 2014 / Revised: 15 May 2014 / Accepted: 27 May 2014 / Published: 30 May 2014
Cited by 6 | PDF Full-text (873 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an experimental study on the nature of permeation properties and pore structure of concrete surface layers containing fly ash. Concretes containing different dosages of fly ash as a replacement for cement (15% and 30% by weight of total cement materials,
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This paper presents an experimental study on the nature of permeation properties and pore structure of concrete surface layers containing fly ash. Concretes containing different dosages of fly ash as a replacement for cement (15% and 30% by weight of total cement materials, respectively) were investigated. Concrete without any fly ash added was also employed as the reference specimen. Laboratory tests were conducted to determine the surface layer properties of concrete including chloride transport, apparent water permeability and pore structure. The results demonstrate that incorporation of fly ash, for the early test period, promotes the chloride ingress at the surface layer of concrete but substituting proportions of fly ash may have little impact on it. With the process of chloride immersion, the chloride concentration at the surface layer of concrete with or without fly ash was found to be nearly the same. In addition, it is suggested that the water permeability at the concrete surface area is closely related to the fly ash contents as well as the chloride exposure time. Pore structure was characterized by means of mercury intrusion porosimetry (MIP) test and the scanning electron microscopy (SEM) images. The modification of pore structure of concrete submersed in distilled water is determined by the pozzolanic reaction of fly ash and the calcium leaching effect. The pozzolanic reaction was more dominant at the immersion time of 180 days while the calcium leaching effect became more evident after 270 days. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Inhibition of Mild Steel Corrosion in Hydrochloric Acid Solution by New Coumarin
Materials 2014, 7(6), 4335-4348; doi:10.3390/ma7064335
Received: 21 October 2013 / Revised: 5 December 2013 / Accepted: 10 April 2014 / Published: 5 June 2014
Cited by 10 | PDF Full-text (568 KB) | HTML Full-text | XML Full-text
Abstract
A new coumarin derivative, N,N′-((2E,2′E)-2,2′-(1,4-phenylenebis (methanylylidene))bis(hydrazinecarbonothioyl))bis(2-oxo-2H-chromene-3-carboxamide) PMBH, was synthesized and its chemical structure was elucidated and confirmed using spectroscopic techniques (Infrared spectroscopy IR, Proton nuclear  magnetic resonance, 1H-NMR and carbon-13 nuclear magnetic resonance 13C-NMR). The corrosion inhibition effect
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A new coumarin derivative, N,N′-((2E,2′E)-2,2′-(1,4-phenylenebis (methanylylidene))bis(hydrazinecarbonothioyl))bis(2-oxo-2H-chromene-3-carboxamide) PMBH, was synthesized and its chemical structure was elucidated and confirmed using spectroscopic techniques (Infrared spectroscopy IR, Proton nuclear  magnetic resonance, 1H-NMR and carbon-13 nuclear magnetic resonance 13C-NMR). The corrosion inhibition effect of PMBH on mild steel in 1.0 M HCl was investigated using corrosion potential (ECORR), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. The obtained results indicated that PMBH has promising inhibitive effects on the corrosion of mild steel in 1.0 M HCl across all of the conditions examined. Scanning electron microscopy (SEM) was used to investigate the morphology of the mild steel before and after immersion in 1.0 M HCl solution containing 0.5 mM of PMBH. Surface analysis revealed improvement of corrosion resistance in presence of PMBH. Full article
Open AccessArticle Notch Corrosion Fatigue Behavior of Ti-6Al-4V
Materials 2014, 7(6), 4349-4366; doi:10.3390/ma7064349
Received: 8 February 2014 / Revised: 9 May 2014 / Accepted: 30 May 2014 / Published: 11 June 2014
Cited by 4 | PDF Full-text (1177 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this paper is to map the corrosion fatigue characteristics of Ti-6Al-4V alloy through the evaluation of the corrosion fatigue initiation and failure mechanisms. The study included the effect of the stress concentration factor at very high Kt values and
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The aim of this paper is to map the corrosion fatigue characteristics of Ti-6Al-4V alloy through the evaluation of the corrosion fatigue initiation and failure mechanisms. The study included the effect of the stress concentration factor at very high Kt values and the role of different inert or corrosive environments. This alloy is widely used in naval-structures and aero-engine communities and the outcomes of the work will have direct relevance to industrial service operations. Axial fatigue tests (R = 0.1; 2 × 105 cycles; f = 10 Hz) were carried out on smooth and high notched (Ktmax = 18.65) flat specimens in laboratory air, paraffin oil, laboratory air + beeswax coating, recirculated 3.5% NaCl solution. The step loading procedure was used to perform the fatigue tests and the surface replica method and crack propagation gages were used to check crack nucleation and propagation until failure. Log-Log plots of σmax vs. Kt showed a bilinear behavior and enabled the demonstration of the presence of a threshold stress intensity factor (Kt = 8–9), after which the environment has no effect on the fatigue damage for all the tested environments. Full article
(This article belongs to the Special Issue Corrosion of Materials)
Open AccessArticle Materials Development for Next Generation Optical Fiber
Materials 2014, 7(6), 4411-4430; doi:10.3390/ma7064411
Received: 22 April 2014 / Revised: 1 June 2014 / Accepted: 3 June 2014 / Published: 11 June 2014
Cited by 13 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
Optical fibers, the enablers of the Internet, are being used in an ever more diverse array of applications. Many of the rapidly growing deployments of fibers are in high-power and, particularly, high power-per-unit-bandwidth systems where well-known optical nonlinearities have historically not been especially
[...] Read more.
Optical fibers, the enablers of the Internet, are being used in an ever more diverse array of applications. Many of the rapidly growing deployments of fibers are in high-power and, particularly, high power-per-unit-bandwidth systems where well-known optical nonlinearities have historically not been especially consequential in limiting overall performance. Today, however, nominally weak effects, most notably stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) are among the principal phenomena restricting continued scaling to higher optical power levels. In order to address these limitations, the optical fiber community has focused dominantly on geometry-related solutions such as large mode area (LMA) designs. Since such scattering, and all other linear and nonlinear optical phenomena including higher order mode instability (HOMI), are fundamentally materials-based in origin, this paper unapologetically advocates material solutions to present and future performance limitations. As such, this paper represents a ‘call to arms’ for material scientists and engineers to engage in this opportunity to drive the future development of optical fibers that address many of the grand engineering challenges of our day. Full article
Open AccessArticle Preparation, Surface and Pore Structure of High Surface Area Activated Carbon Fibers from Bamboo by Steam Activation
Materials 2014, 7(6), 4431-4441; doi:10.3390/ma7064431
Received: 5 February 2014 / Revised: 19 May 2014 / Accepted: 28 May 2014 / Published: 12 June 2014
Cited by 16 | PDF Full-text (745 KB) | HTML Full-text | XML Full-text
Abstract
High surface area activated carbon fibers (ACF) have been prepared from bamboo by steam activation after liquefaction and curing. The influences of activation temperature on the microstructure, surface area and porosity were investigated. The results showed that ACF from bamboo at 850 °C
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High surface area activated carbon fibers (ACF) have been prepared from bamboo by steam activation after liquefaction and curing. The influences of activation temperature on the microstructure, surface area and porosity were investigated. The results showed that ACF from bamboo at 850 °C have the maximum iodine and methylene blue adsorption values. Aside from the graphitic carbon, phenolic and carbonyl groups were the predominant functions on the surface of activated carbon fiber from bamboo. The prepared ACF from bamboo were found to be mainly type I of isotherm, but the mesoporosity presented an increasing trend after 700 °C. The surface area and micropore volume of samples, which were determined by application of the Brunauer-Emmett-Teller (BET) and t-plot methods, were as high as 2024 m2/g and 0.569 cm3/g, respectively. It was also found that the higher activation temperature produced the more ordered microcrystalline structure of ACF from bamboo. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle Theoretical Estimation of Thermal Effects in Drilling of Woven Carbon Fiber Composite
Materials 2014, 7(6), 4442-4454; doi:10.3390/ma7064442
Received: 10 March 2014 / Revised: 24 May 2014 / Accepted: 29 May 2014 / Published: 12 June 2014
Cited by 5 | PDF Full-text (1501 KB) | HTML Full-text | XML Full-text
Abstract
Carbon Fiber Reinforced Polymer (CFRPs) composites are extensively used in structural applications due to their attractive properties. Although the components are usually made near net shape, machining processes are needed to achieve dimensional tolerance and assembly requirements. Drilling is a common operation required
[...] Read more.
Carbon Fiber Reinforced Polymer (CFRPs) composites are extensively used in structural applications due to their attractive properties. Although the components are usually made near net shape, machining processes are needed to achieve dimensional tolerance and assembly requirements. Drilling is a common operation required for further mechanical joining of the components. CFRPs are vulnerable to processing induced damage; mainly delamination, fiber pull-out, and thermal degradation, drilling induced defects being one of the main causes of component rejection during manufacturing processes. Despite the importance of analyzing thermal phenomena involved in the machining of composites, only few authors have focused their attention on this problem, most of them using an experimental approach. The temperature at the workpiece could affect surface quality of the component and its measurement during processing is difficult. The estimation of the amount of heat generated during drilling is important; however, numerical modeling of drilling processes involves a high computational cost. This paper presents a combined approach to thermal analysis of composite drilling, using both an analytical estimation of heat generated during drilling and numerical modeling for heat propagation. Promising results for indirect detection of risk of thermal damage, through the measurement of thrust force and cutting torque, are obtained. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
Open AccessArticle Preparation and Characterization of Li-Ion Graphite Anodes Using Synchrotron Tomography
Materials 2014, 7(6), 4455-4472; doi:10.3390/ma7064455
Received: 31 March 2014 / Revised: 26 May 2014 / Accepted: 28 May 2014 / Published: 12 June 2014
Cited by 8 | PDF Full-text (3836 KB) | HTML Full-text | XML Full-text
Abstract
We present an approach for multi-layer preparation to perform microstructure analysis of a Li-ion cell anode active material using synchrotron tomography. All necessary steps, from the disassembly of differently-housed cells (pouch and cylindrical), via selection of interesting layer regions, to the separation of
[...] Read more.
We present an approach for multi-layer preparation to perform microstructure analysis of a Li-ion cell anode active material using synchrotron tomography. All necessary steps, from the disassembly of differently-housed cells (pouch and cylindrical), via selection of interesting layer regions, to the separation of the graphite-compound and current collector, are described in detail. The proposed stacking method improves the efficiency of synchrotron tomography by measuring up to ten layers in parallel, without the loss of image resolution nor quality, resulting in a maximization of acquired data. Additionally, we perform an analysis of the obtained 3D volumes by calculating microstructural characteristics, like porosity, tortuosity and specific surface area. Due to a large amount of measurable layers within one stacked sample, differences between aged and pristine material (e.g., significant differences in tortuosity and specific surface area, while porosity remains constant), as well as the homogeneity of the material within one cell could be recognized. Full article
(This article belongs to the Special Issue New Energy Materials)
Open AccessArticle A Comparative Study of the Adsorption of Methylene Blue onto Synthesized Nanoscale Zero-Valent Iron-Bamboo and Manganese-Bamboo Composites
Materials 2014, 7(6), 4493-4507; doi:10.3390/ma7064493
Received: 1 April 2014 / Revised: 13 May 2014 / Accepted: 23 May 2014 / Published: 12 June 2014
Cited by 8 | PDF Full-text (1698 KB) | HTML Full-text | XML Full-text
Abstract
In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo
[...] Read more.
In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites. Full article
(This article belongs to the Special Issue Advances in Nanoporous Materials)
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Open AccessArticle Effect of Organo-Modified Nanoclay on the Thermal and Bulk Structural Properties of Poly(3-hydroxybutyrate)-Epoxidized Natural Rubber Blends: Formation of Multi-Components Biobased Nanohybrids
Materials 2014, 7(6), 4508-4523; doi:10.3390/ma7064508
Received: 7 December 2013 / Revised: 14 May 2014 / Accepted: 20 May 2014 / Published: 13 June 2014
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Abstract
Multi-component nanohybrids comprising of organo-modified montmorillonite (MMT) and immiscible biopolymer blends of poly(3-hydroxybutyrate) (PHB) and epoxidized natural rubber (ENR-50) were prepared by solvent casting technique. The one and three dimensional morphology of PHB/ENR-50/MMT systems were studied using Polarizing Optical Microscopy (POM) and Scanning
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Multi-component nanohybrids comprising of organo-modified montmorillonite (MMT) and immiscible biopolymer blends of poly(3-hydroxybutyrate) (PHB) and epoxidized natural rubber (ENR-50) were prepared by solvent casting technique. The one and three dimensional morphology of PHB/ENR-50/MMT systems were studied using Polarizing Optical Microscopy (POM) and Scanning Electron Microscopy (SEM). Differential scanning calorimetry (DSC) technique was used to evaluate the thermal properties of the nanohybrids. The melting temperature (Tm) and enthalpy of melting (ΔHm) of PHB decrease with respect to the increase in ENR-50 as well as MMT content. The non-isothermal decomposition of the nanohybrids was studied using thermogravimetric (TG-DTG) analysis. FTIR-ATR spectra supported ring opening of the epoxide group via reaction with carboxyl group of PHB and amines of organic modifier. The reaction mechanism towards the formation of the nanohybrids is proposed. Full article
Open AccessArticle Improving the Pass-Band Return Loss in Liquid Crystal Dual-Mode Bandpass Filters by Microstrip Patch Reshaping
Materials 2014, 7(6), 4524-4535; doi:10.3390/ma7064524
Received: 28 February 2014 / Revised: 1 April 2014 / Accepted: 3 June 2014 / Published: 13 June 2014
PDF Full-text (998 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the design and experimental characterization of a tunable microstrip bandpass filter based on liquid crystal technology are presented. A reshaped microstrip dual-mode filter structure has been used in order to improve the device performance. Specifically, the aim is to increase
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In this paper, the design and experimental characterization of a tunable microstrip bandpass filter based on liquid crystal technology are presented. A reshaped microstrip dual-mode filter structure has been used in order to improve the device performance. Specifically, the aim is to increase the pass-band return loss of the filter by narrowing the filter bandwidth. Simulations confirm the improvement of using this new structure, achieving a pass-band return loss increase of 1.5 dB at least. Because of the anisotropic properties of LC molecules, a filter central frequency shift from 4.688 GHz to 5.045 GHz, which means a relative tuning range of 7.3%, is measured when an external AC voltage from 0 Vrms to 15 Vrms is applied to the device. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessArticle Fundamental Study on the Development of Structural Lightweight Concrete by Using Normal Coarse Aggregate and Foaming Agent
Materials 2014, 7(6), 4536-4554; doi:10.3390/ma7064536
Received: 6 May 2014 / Revised: 3 June 2014 / Accepted: 3 June 2014 / Published: 13 June 2014
Cited by 2 | PDF Full-text (1076 KB) | HTML Full-text | XML Full-text
Abstract
Structural lightweight concrete (SLWC) has superior properties that allow the optimization of super tall structure systems for the process of design. Because of the limited supply of lightweight aggregates in Korea, the development of structural lightweight concrete without lightweight aggregates is needed. The
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Structural lightweight concrete (SLWC) has superior properties that allow the optimization of super tall structure systems for the process of design. Because of the limited supply of lightweight aggregates in Korea, the development of structural lightweight concrete without lightweight aggregates is needed. The physical and mechanical properties of specimens that were cast using normal coarse aggregates and different mixing ratios of foaming agent to evaluate the possibility of creating structural lightweight concrete were investigated. The results show that the density of SLWC decreases as the dosage of foaming agent increases up to a dosage of 0.6%, as observed by SEM. It was also observed that the foaming agent induced well separated pores, and that the size of the pores ranged from 50 to 100 μm. Based on the porosity of concrete specimens with foaming agent, compressive strength values of structural lightweight foam concrete (SLWFC) were obtained. It was also found that the estimated values from proposed equations for compressive strength and modulus of elasticity of SLWFC, and values obtained by actual measurements were in good agreement. Thus, this study confirms that new structural lightweight concrete using normal coarse aggregates and foaming agent can be developed successfully. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle Characterization of Printed Circuit Boards for Metal and Energy Recovery after Milling and Mechanical Separation
Materials 2014, 7(6), 4555-4566; doi:10.3390/ma7064555
Received: 1 April 2014 / Revised: 13 May 2014 / Accepted: 3 June 2014 / Published: 16 June 2014
Cited by 5 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
The proper disposal of electrical and electronic waste is currently a concern of researchers and environmental managers not only because of the large volume of such waste generated, but also because of the heavy metals and toxic substances it contains. This study analyzed
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The proper disposal of electrical and electronic waste is currently a concern of researchers and environmental managers not only because of the large volume of such waste generated, but also because of the heavy metals and toxic substances it contains. This study analyzed printed circuit boards (PCBs) from discarded computers to determine their metal content and characterized them as solid waste and fuel. The analysis showed that PCBs consist of approximately 26% metal, made up mainly of copper, lead, aluminum, iron and tin, as well as other heavy metals such as cadmium and nickel. Comparison with the results of other studies indicated that the concentration of precious metals (gold and silver) has declined over time. Analysis of the leachate revealed high concentrations of cadmium and lead, giving the residue the characteristics of hazardous waste. After milling the PCBs, we found that larger amounts of metal were concentrated in smaller fractions, while the lightest fraction, obtained by density separation, had a gross calorific value of approximately 11 MJ/kg, although with a high ash content. Milling followed by density separation proved potentially useful for recovery of metals and energy-rich fractions. Full article
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Open AccessArticle Superlattice Microstructured Optical Fiber
Materials 2014, 7(6), 4567-4573; doi:10.3390/ma7064567
Received: 9 May 2014 / Revised: 4 June 2014 / Accepted: 4 June 2014 / Published: 16 June 2014
Cited by 2 | PDF Full-text (361 KB) | HTML Full-text | XML Full-text
Abstract
A generic three-stage stack-and-draw method is demonstrated for the fabrication of complex-microstructured optical fibers. We report the fabrication and characterization of a silica superlattice microstructured fiber with more than 800 rhomboidally arranged air-holes. A polarization-maintaining fiber with a birefringence of 8.5 × 10
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A generic three-stage stack-and-draw method is demonstrated for the fabrication of complex-microstructured optical fibers. We report the fabrication and characterization of a silica superlattice microstructured fiber with more than 800 rhomboidally arranged air-holes. A polarization-maintaining fiber with a birefringence of 8.5 × 10−4 is demonstrated. The birefringent property of the fiber is found to be highly insensitive to external environmental effects, such as pressure. Full article
Open AccessArticle Damping Characteristics of Ti50Ni50−xCux (x = 0~30 at.%) Shape Memory Alloys at a Low Frequency
Materials 2014, 7(6), 4574-4586; doi:10.3390/ma7064574
Received: 27 February 2014 / Revised: 3 April 2014 / Accepted: 11 June 2014 / Published: 16 June 2014
Cited by 2 | PDF Full-text (2493 KB) | HTML Full-text | XML Full-text
Abstract
The damping characteristics of Ti50Ni50−xCux (x = 0~30 at.%) shape memory alloys (SMAs) at a low frequency have been studied using a dynamic mechanical analyzer. The magnitude of the tan δ value and the values of
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The damping characteristics of Ti50Ni50−xCux (x = 0~30 at.%) shape memory alloys (SMAs) at a low frequency have been studied using a dynamic mechanical analyzer. The magnitude of the tan δ value and the values of the storage modulus (E0) softening/hardening and the strain variation exhibited in B2↔B19 transformation are all higher than those in B2↔B19’ transformation. The larger E0 softening/hardening in B2↔B19 can induce higher strain variation in this transformation. It is suggested that the greater mobility of the twin boundaries and the larger magnitude of the strain variation both cause the higher tan δ value exhibited in B2↔B19 transformation, as compared with B2↔B19’ transformation. In comparison with that in B19’ martensite, the E0 value in B19 martensite is low and not affected so greatly by changes in temperature. Relaxation peaks are observed in B19’ martensite, but not in B19 martensite, because the latter has rare twinned variants. The activation energy of the relaxation peak is calculated and found to increase as the Cu-content increases in these SMAs. Full article
(This article belongs to the Special Issue Shape Memory Materials)
Open AccessArticle Facile Solvothermal Synthesis and Gas Sensitivity of Graphene/WO3 Nanocomposites
Materials 2014, 7(6), 4587-4600; doi:10.3390/ma7064587
Received: 1 May 2014 / Revised: 9 June 2014 / Accepted: 9 June 2014 / Published: 17 June 2014
Cited by 8 | PDF Full-text (882 KB) | HTML Full-text | XML Full-text
Abstract
Graphene has attracted enormous attention owing to its extraordinary properties, while graphene-based nanocomposites hold promise for many applications. In this paper, we present a two-step exploitation method for preparation of graphene oxides and a facile solvothermal route for preparation of few-layer graphene nanosheets
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Graphene has attracted enormous attention owing to its extraordinary properties, while graphene-based nanocomposites hold promise for many applications. In this paper, we present a two-step exploitation method for preparation of graphene oxides and a facile solvothermal route for preparation of few-layer graphene nanosheets and graphene/WO3 nanocomposites in an ethanol-distilled water medium. The as-synthesized samples were characterized by using field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA) and gas-sensing test. The resistivity of the thick-film gas sensors based on sandwich-like graphene/WO3 nanocomposites can be controlled by varying the amount of graphene in the composites. Graphene/WO3 nanocomposites with graphene content higher than 1% show fast response, high selectivity and fine sensitivity to NOx. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle The Micropillar Structure on Silk Fibroin Film Influence Intercellular Connection Mediated by Nanotubular Structures
Materials 2014, 7(6), 4628-4639; doi:10.3390/ma7064628
Received: 10 April 2014 / Revised: 28 May 2014 / Accepted: 9 June 2014 / Published: 18 June 2014
Cited by 1 | PDF Full-text (2084 KB) | XML Full-text
Abstract
Tunneling nanotubes are important membrane channels for cell-to-cell communication. In this study, we investigated the effect of the microenvironment on nanotubular structures by preparing a three-dimensional silk fibroin micropillar structure. In previous reports, tunneling nanotubes were described as stretched membrane channels between interconnected
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Tunneling nanotubes are important membrane channels for cell-to-cell communication. In this study, we investigated the effect of the microenvironment on nanotubular structures by preparing a three-dimensional silk fibroin micropillar structure. In previous reports, tunneling nanotubes were described as stretched membrane channels between interconnected cells at their nearest distance. They hover freely in the cell culture medium and do not contact with the substratum. Interestingly, the micropillars could provide supporting points for nanotubular connection on silk fibroin films, where nanotubular structure formed a stable anchor at contact points. Consequently, the extension direction of nanotubular structure was affected by the micropillar topography. This result suggests that the hovering tunneling nanotubes in the culture medium will come into contact with the raised roadblock on the substrates during long-distance extension. These findings imply that the surface microtopography of biomaterials have an important influence on cell communication mediated by tunneling nanotubes. Full article
Open AccessArticle Improved Strength and Toughness of Carbon Woven Fabric Composites with Functionalized MWCNTs
Materials 2014, 7(6), 4640-4657; doi:10.3390/ma7064640
Received: 28 February 2014 / Revised: 11 April 2014 / Accepted: 4 June 2014 / Published: 18 June 2014
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Abstract
This investigation examines the role of carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs) in the on- and off-axis flexure and the shear responses of thin carbon woven fabric composite plates. The chemically functionalized COOH-MWCNTs were used to fabricate epoxy nanocomposites and, subsequently, carbon woven
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This investigation examines the role of carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs) in the on- and off-axis flexure and the shear responses of thin carbon woven fabric composite plates. The chemically functionalized COOH-MWCNTs were used to fabricate epoxy nanocomposites and, subsequently, carbon woven fabric plates to be tested on flexure and shear. In addition to the neat epoxy, three loadings of COOH-MWCNTs were examined: 0.5 wt%, 1.0 wt% and 1.5 wt% of epoxy. While no significant statistical difference in the flexure response of the on-axis specimens was observed, significant increases in the flexure strength, modulus and toughness of the off-axis specimens were observed. The average increase in flexure strength and flexure modulus with the addition of 1.5 wt% COOH-MWCNTs improved by 28% and 19%, respectively. Finite element modeling is used to demonstrate fiber domination in on-axis flexure behavior and matrix domination in off-axis flexure behavior. Furthermore, the 1.5 wt% COOH-MWCNTs increased the toughness of carbon woven composites tested on shear by 33%. Microstructural investigation using Fourier Transform Infrared Spectroscopy (FTIR) proves the existence of chemical bonds between the COOH-MWCNTs and the epoxy matrix. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
Open AccessArticle Two Octaves Supercontinuum Generation in Lead-Bismuth Glass Based Photonic Crystal Fiber
Materials 2014, 7(6), 4658-4668; doi:10.3390/ma7064658
Received: 21 April 2014 / Revised: 5 June 2014 / Accepted: 9 June 2014 / Published: 19 June 2014
Cited by 5 | PDF Full-text (611 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we report a two octave spanning supercontinuum generation in a bandwidth of 700–3000 nm in a single-mode photonic crystal fiber made of lead-bismuth-gallate glass. To our knowledge this is the broadest supercontinuum reported in heavy metal oxide glass based fibers.
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In this paper we report a two octave spanning supercontinuum generation in a bandwidth of 700–3000 nm in a single-mode photonic crystal fiber made of lead-bismuth-gallate glass. To our knowledge this is the broadest supercontinuum reported in heavy metal oxide glass based fibers. The fiber was fabricated using an in-house synthesized glass with optimized nonlinear, rheological and transmission properties in the range of 500–4800 nm. The photonic cladding consists of 8 rings of air holes. The fiber has a zero dispersion wavelength (ZDW) at 1460 nm. Its dispersion is determined mainly by the first ring of holes in the cladding with a relative hole size of 0.73. Relative hole size of the remaining seven rings is 0.54, which allows single mode performance of the fiber in the infrared range and reduces attenuation of the fundamental mode. The fiber is pumped into anomalous dispersion with 150 fs pulses at 1540 nm. Observed spectrum of 700–3000 nm was generated in 2 cm of fiber with pulse energy below 4 nJ. A flatness of 5 dB was observed in 950–2500 nm range. Full article
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Open AccessArticle Corrosion Prevention of Aluminum Nanoparticles by a Polyurethane Coating
Materials 2014, 7(6), 4710-4722; doi:10.3390/ma7064710
Received: 28 January 2014 / Revised: 28 May 2014 / Accepted: 9 June 2014 / Published: 19 June 2014
Cited by 3 | PDF Full-text (839 KB) | HTML Full-text | XML Full-text
Abstract
In order to prevent corrosion, aluminum nanoparticles were coated with a polyurethane polymer. The coverage of the polyurethane polymer was controlled from 0 to 100%, which changed the corrosion rate of the nanoparticles quantitatively. The surface of the polymer coating was investigated by
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In order to prevent corrosion, aluminum nanoparticles were coated with a polyurethane polymer. The coverage of the polyurethane polymer was controlled from 0 to 100%, which changed the corrosion rate of the nanoparticles quantitatively. The surface of the polymer coating was investigated by Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM), and the corrosion resistance of the nanoparticles was estimated by a wet/dry corrosion test on a Pt plate with a NaCl solution. From a TEM with EDAX analysis, the 10 mass% polymer coated Al particles in the synthesis were almost 100% covered on the surface by a polymer film of 10 nm thick. On the other hand, the 3 mass% polymer coated Al was almost 40% covered by a film. In the AFM, the potential around the Al particles had a relatively low value with the polymer coating, which indicated that the conductivity of the Al was isolated from the Pt plate by the polymer. Both the corrosion and H2 evolution reaction rates were quantitatively reduced by the mass% of polymer coating. In the case of the 10 mass% coated sample, there was no corrosion of Al nanoparticles. This fact suggested that the electrochemical reaction was suppressed by the polymer coating. Moreover, the reaction rate of Al nanoparticles was suppressed in proportion to the coverage percentage of the coating. Thus, to conclude, it was found that the corrosion rate of Al nanoparticles could be quantitatively suppressed by the coverage percentage of the polymer coating. Full article
(This article belongs to the Special Issue Corrosion of Materials)
Open AccessArticle Ytterbium-Phosphate Glass for Microstructured Fiber Laser
Materials 2014, 7(6), 4723-4738; doi:10.3390/ma7064723
Received: 5 May 2014 / Revised: 11 June 2014 / Accepted: 11 June 2014 / Published: 19 June 2014
Cited by 3 | PDF Full-text (1128 KB) | HTML Full-text | XML Full-text
Abstract
In the paper, we report on the development of a synthesis and melting method of phosphate glasses designed for active microstructured fiber manufacturing. Non-doped glass synthesized in a P2O5-Al2O3-BaO-ZnO-MgO-Na2O oxide system served as
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In the paper, we report on the development of a synthesis and melting method of phosphate glasses designed for active microstructured fiber manufacturing. Non-doped glass synthesized in a P2O5-Al2O3-BaO-ZnO-MgO-Na2O oxide system served as the matrix material; meanwhile, the glass was doped with 6 mol% (18 wt%) of Yb2O3, as fiber core. The glasses were well-fitted in relation to optical (refractive index) and thermal proprieties (thermal expansion coefficient, rheology). The fiber with the Yb3+-doped core, with a wide internal photonic microstructure for a laser pump, as well as with a high relative hole size in the photonic outer air-cladding, was produced. The laser built on the basis of this fiber enabled achieving 8.07 W of output power with 20.5% slope efficiency against the launched pump power, in single-mode operation M2 = 1.59, from a 53 cm-long cavity. Full article
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Open AccessArticle Influence of Aggregate Coated with Modified Sulfur on the Properties of Cement Concrete
Materials 2014, 7(6), 4739-4754; doi:10.3390/ma7064739
Received: 21 April 2014 / Revised: 10 June 2014 / Accepted: 10 June 2014 / Published: 20 June 2014
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Abstract
This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA) to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to
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This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA) to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to coat the aggregate surface at a speed of 20 rpm for 120 s. The MSCA with modified sulfur corresponding to 5% of the cement weight did not significantly affect the flexural strength in a prism concrete beam specimen, regardless of the water-cement ratio (W/C). However, a dosage of more than 7.5% decreased the flexural strength. On the other hand, the MSCA considerably improved the resistance to the sulfuric acid and the freezing-thawing, regardless of the sulfur dosage in the MSCA. The coating modified sulfur of 5% dosage consequently led to good results for the mechanical properties and durability of MSCA concrete. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides
Materials 2014, 7(6), 4755-4772; doi:10.3390/ma7064755
Received: 13 February 2014 / Revised: 19 March 2014 / Accepted: 12 June 2014 / Published: 20 June 2014
Cited by 7 | PDF Full-text (3068 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects
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The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO2 leads to a satisfactory surface appearance compared to that of the TIG weld made with Al2O3. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO2, the TIG welding with nanoparticle SiO2 has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al2O3 does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO2 uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al2O3 results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides. Full article
Open AccessArticle Sintering Behaviour of Waste Olivine and Olivine/Alumina Blends
Materials 2014, 7(6), 4773-4788; doi:10.3390/ma7064773
Received: 23 April 2014 / Revised: 9 June 2014 / Accepted: 10 June 2014 / Published: 20 June 2014
Cited by 1 | PDF Full-text (1438 KB) | HTML Full-text | XML Full-text
Abstract
The sintering behaviour of several green compacts made with olivine or olivine/alumina powder blends has been examined. To this goal, powders were attrition milled, uniaxially pressed into specimens and air sintered at temperatures ranging from 1100 to 1300 °C. The resulting samples were
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The sintering behaviour of several green compacts made with olivine or olivine/alumina powder blends has been examined. To this goal, powders were attrition milled, uniaxially pressed into specimens and air sintered at temperatures ranging from 1100 to 1300 °C. The resulting samples were characterized by water absorption, shrinkage, phase composition and density. Compositions containing 5%, 10% and 20% Al2O3 have a sintering behaviour similar to that of olivine alone, reaching low residual porosity when fired at 1300 °C. Conversely, the composition containing 40% Al2O3 displays an almost flat shrinkage profile and maintains high residual porosity in the examined temperature range. Full article
Open AccessArticle Photostability of 2D Organic-Inorganic Hybrid Perovskites
Materials 2014, 7(6), 4789-4802; doi:10.3390/ma7064789
Received: 11 May 2014 / Revised: 12 June 2014 / Accepted: 13 June 2014 / Published: 20 June 2014
Cited by 10 | PDF Full-text (521 KB) | HTML Full-text | XML Full-text
Abstract
We analyze the behavior of a series of newly synthesized (R-NH3)2PbX4 perovskites and, in particular, discuss the possible reasons which cause their degradation under UV illumination. Experimental results show that the degradation process depends a lot on their
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We analyze the behavior of a series of newly synthesized (R-NH3)2PbX4 perovskites and, in particular, discuss the possible reasons which cause their degradation under UV illumination. Experimental results show that the degradation process depends a lot on their molecular components: not only the inorganic part, but also the chemical structure of the organic moieties play an important role in bleaching and photo-chemical reaction processes which tend to destroy perovskites luminescent framework. In addition, we find the spatial arrangement in crystal also influences the photostability course. Following these trends, we propose a plausible mechanism for the photodegradation of the films, and also introduced options for optimized stability. Full article
(This article belongs to the Special Issue Opto-Electronic Materials)
Open AccessArticle Manufacturing and Characterization of Ti6Al4V Lattice Components Manufactured by Selective Laser Melting
Materials 2014, 7(6), 4803-4822; doi:10.3390/ma7064803
Received: 30 April 2014 / Revised: 6 June 2014 / Accepted: 16 June 2014 / Published: 23 June 2014
Cited by 8 | PDF Full-text (1847 KB) | HTML Full-text | XML Full-text
Abstract
The paper investigates the fabrication of Selective Laser Melting (SLM) titanium alloy Ti6Al4V micro-lattice structures for the production of lightweight components. Specifically, the pillar textile unit cell is used as base lattice structure and alternative lattice topologies including reinforcing vertical bars are also
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The paper investigates the fabrication of Selective Laser Melting (SLM) titanium alloy Ti6Al4V micro-lattice structures for the production of lightweight components. Specifically, the pillar textile unit cell is used as base lattice structure and alternative lattice topologies including reinforcing vertical bars are also considered. Detailed characterizations of dimensional accuracy, surface roughness, and micro-hardness are performed. In addition, compression tests are carried out in order to evaluate the mechanical strength and the energy absorbed per unit mass of the lattice truss specimens made by SLM. The built structures have a relative density ranging between 0.2234 and 0.5822. An optimization procedure is implemented via the method of Taguchi to identify the optimal geometric configuration which maximizes peak strength and energy absorbed per unit mass. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
Open AccessArticle Application of Hydrophilic Silanol-Based Chemical Grout for Strengthening Damaged Reinforced Concrete Flexural Members
Materials 2014, 7(6), 4823-4844; doi:10.3390/ma7064823
Received: 28 February 2014 / Revised: 26 March 2014 / Accepted: 13 June 2014 / Published: 23 June 2014
Cited by 3 | PDF Full-text (1067 KB) | HTML Full-text | XML Full-text
Abstract
In this study, hydrophilic chemical grout using silanol (HCGS) was adopted to overcome the performance limitations of epoxy materials used for strengthening existing buildings and civil engineering structures. The enhanced material performances of HCGS were introduced, and applied to the section enlargement method,
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In this study, hydrophilic chemical grout using silanol (HCGS) was adopted to overcome the performance limitations of epoxy materials used for strengthening existing buildings and civil engineering structures. The enhanced material performances of HCGS were introduced, and applied to the section enlargement method, which is one of the typical structural strengthening methods used in practice. To evaluate the excellent structural strengthening performance of the HCGS, structural tests were conducted on reinforced concrete beams, and analyses on the flexural behaviors of test specimens were performed by modified partial interaction theory (PIT). In particular, to improve the constructability of the section enlargement method, an advanced strengthening method was proposed, in which the precast panel was directly attached to the bottom of the damaged structural member by HCGS, and the degree of connection of the test specimens, strengthened by the section enlargement method, were quantitatively evaluated by PIT-based analysis. Full article
(This article belongs to the Special Issue Construction Materials)
Open AccessArticle Mechanical and Electrical Characterization of Entangled Networks of Carbon Nanofibers
Materials 2014, 7(6), 4845-4853; doi:10.3390/ma7064845
Received: 1 March 2014 / Revised: 23 May 2014 / Accepted: 3 June 2014 / Published: 23 June 2014
Cited by 4 | PDF Full-text (587 KB) | HTML Full-text | XML Full-text
Abstract
Entangled networks of carbon nanofibers are characterized both mechanically and electrically. Results for both tensile and compressive loadings of the entangled networks are presented for various densities. Mechanically, the nanofiber ensembles follow the micromechanical model originally proposed by van Wyk nearly 70 years
[...] Read more.
Entangled networks of carbon nanofibers are characterized both mechanically and electrically. Results for both tensile and compressive loadings of the entangled networks are presented for various densities. Mechanically, the nanofiber ensembles follow the micromechanical model originally proposed by van Wyk nearly 70 years ago. Interpretations are given on the mechanisms occurring during loading and unloading of the carbon nanofiber components. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
Open AccessArticle Static and Dynamic Characteristics of a Long-Span Cable-Stayed Bridge with CFRP Cables
Materials 2014, 7(6), 4854-4877; doi:10.3390/ma7064854
Received: 21 March 2014 / Revised: 25 May 2014 / Accepted: 12 June 2014 / Published: 23 June 2014
Cited by 4 | PDF Full-text (2975 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the scope of CFRP cables in cable-stayed bridges is studied by establishing a numerical model of a 1400-m span of the same. The mechanical properties and characteristics of CFRP stay cables and of a cable-stayed bridge with CFRP cables are
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In this study, the scope of CFRP cables in cable-stayed bridges is studied by establishing a numerical model of a 1400-m span of the same. The mechanical properties and characteristics of CFRP stay cables and of a cable-stayed bridge with CFRP cables are here subjected to comprehensive analysis. The anomalies in the damping properties of free vibration, nonlinear parametric vibration and wind fluctuating vibration between steel cables and CFRP cables are determined. The structural stiffness, wind resistance and traffic vibration of the cable-stayed bridge with CFRP cables are also analyzed. It was found that the static performances of a cable-stayed bridge with CFRP cables and steel cables are basically the same. The natural frequencies of CFRP cables do not coincide with the major natural frequencies of the cable-stayed bridge, so the likelihood of CFRP cable-bridge coupling vibration is minuscule. For CFRP cables, the response amplitudes of both parametric vibration and wind fluctuating vibration are smaller than those of steel cables. It can be concluded from the research that the use of CFRP cables does not change the dynamic characteristics of the vehicle-bridge coupling vibration. Therefore, they can be used in long-span cable-stayed bridges with an excellent mechanical performance. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available

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Open AccessReview Characterization of Nanoreinforcement Dispersion in Inorganic Nanocomposites: A Review
Materials 2014, 7(6), 4148-4181; doi:10.3390/ma7064148
Received: 20 April 2014 / Revised: 14 May 2014 / Accepted: 15 May 2014 / Published: 28 May 2014
Cited by 7 | PDF Full-text (9883 KB) | HTML Full-text | XML Full-text
Abstract
Metal and ceramic matrix composites have been developed to enhance the stiffness and strength of metals and alloys, and improve the toughness of monolithic ceramics, respectively. It is possible to further improve their properties by using nanoreinforcement, which led to the development of
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Metal and ceramic matrix composites have been developed to enhance the stiffness and strength of metals and alloys, and improve the toughness of monolithic ceramics, respectively. It is possible to further improve their properties by using nanoreinforcement, which led to the development of metal and ceramic matrix nanocomposites, in which case, the dimension of the reinforcement is on the order of nanometer, typically less than 100 nm. However, in many cases, the properties measured experimentally remain far from those estimated theoretically. This is mainly due to the fact that the properties of nanocomposites depend not only on the properties of the individual constituents, i.e., the matrix and reinforcement as well as the interface between them, but also on the extent of nanoreinforcement dispersion. Therefore, obtaining a uniform dispersion of the nanoreinforcement in the matrix remains a key issue in the development of nanocomposites with the desired properties. The issue of nanoreinforcement dispersion was not fully addressed in review papers dedicated to processing, characterization, and properties of inorganic nanocomposites. In addition, characterization of nanoparticles dispersion, reported in literature, remains largely qualitative. The objective of this review is to provide a comprehensive description of characterization techniques used to evaluate the extent of nanoreinforcement dispersion in inorganic nanocomposites and critically review published work. Moreover, methodologies and techniques used to characterize reinforcement dispersion in conventional composites, which may be used for quantitative characterization of nanoreinforcement dispersion in nanocomposites, is also presented. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessReview Nanoporous Anodic Alumina: A Versatile Platform for Optical Biosensors
Materials 2014, 7(6), 4297-4320; doi:10.3390/ma7064297
Received: 19 April 2014 / Revised: 24 May 2014 / Accepted: 27 May 2014 / Published: 30 May 2014
Cited by 34 | PDF Full-text (2577 KB) | HTML Full-text | XML Full-text
Abstract
Nanoporous anodic alumina (NAA) has become one of the most promising nanomaterials in optical biosensing as a result of its unique physical and chemical properties. Many studies have demonstrated the outstanding capabilities of NAA for developing optical biosensors in combination with different optical
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Nanoporous anodic alumina (NAA) has become one of the most promising nanomaterials in optical biosensing as a result of its unique physical and chemical properties. Many studies have demonstrated the outstanding capabilities of NAA for developing optical biosensors in combination with different optical techniques. These results reveal that NAA is a promising alternative to other widely explored nanoporous platforms, such as porous silicon. This review is aimed at reporting on the recent advances and current stage of development of NAA-based optical biosensing devices. The different optical detection techniques, principles and concepts are described in detail along with relevant examples of optical biosensing devices using NAA sensing platforms. Furthermore, we summarise the performance of these devices and provide a future perspective on this promising research field. Full article
(This article belongs to the Special Issue Advanced Nanomaterials for Biosensors)
Open AccessReview Bioceramics for Hip Joints: The Physical Chemistry Viewpoint
Materials 2014, 7(6), 4367-4410; doi:10.3390/ma7064367
Received: 1 April 2014 / Revised: 14 May 2014 / Accepted: 26 May 2014 / Published: 11 June 2014
Cited by 6 | PDF Full-text (2050 KB) | HTML Full-text | XML Full-text
Abstract
Which intrinsic biomaterial parameter governs and, if quantitatively monitored, could reveal to us the actual lifetime potential of advanced hip joint bearing materials? An answer to this crucial question is searched for in this paper, which identifies ceramic bearings as the most innovative
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Which intrinsic biomaterial parameter governs and, if quantitatively monitored, could reveal to us the actual lifetime potential of advanced hip joint bearing materials? An answer to this crucial question is searched for in this paper, which identifies ceramic bearings as the most innovative biomaterials in hip arthroplasty. It is shown that, if in vivo exposures comparable to human lifetimes are actually searched for, then fundamental issues should lie in the physical chemistry aspects of biomaterial surfaces. Besides searching for improvements in the phenomenological response of biomaterials to engineering protocols, hip joint components should also be designed to satisfy precise stability requirements in the stoichiometric behavior of their surfaces when exposed to extreme chemical and micromechanical conditions. New spectroscopic protocols have enabled us to visualize surface stoichiometry at the molecular scale, which is shown to be the key for assessing bioceramics with elongated lifetimes with respect to the primitive alumina biomaterials used in the past. Full article
(This article belongs to the Special Issue Ceramics for Healthcare 2013)
Open AccessReview Biological Activation of Inert Ceramics: Recent Advances Using Tailored Self-Assembled Monolayers on Implant Ceramic Surfaces
Materials 2014, 7(6), 4473-4492; doi:10.3390/ma7064473
Received: 1 April 2014 / Revised: 20 May 2014 / Accepted: 5 June 2014 / Published: 12 June 2014
Cited by 5 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies
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High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies have been investigated over the last couple of years. One promising approach investigates the technique of Self-Assembled Monolayers (SAM) and subsequent chemical functionalization to create a biologically active tissue-facing surface layer. Implementation of this would have a beneficial impact on several fields in modern implant medicine such as hip and knee arthroplasty, dental applications and related fields. This review aims to give a summarizing overview of the latest advances in this recently emerging field, along with thorough introductions of the underlying mechanism of SAMs and surface cell attachment mechanics on the cell side. Full article
(This article belongs to the Special Issue Ceramics for Healthcare 2013)
Open AccessReview From Cellulosic Based Liquid Crystalline Sheared Solutions to 1D and 2D Soft Materials
Materials 2014, 7(6), 4601-4627; doi:10.3390/ma7064601
Received: 30 March 2014 / Revised: 26 May 2014 / Accepted: 10 June 2014 / Published: 18 June 2014
Cited by 2 | PDF Full-text (1592 KB) | HTML Full-text | XML Full-text
Abstract
Liquid crystalline cellulosic-based solutions described by distinctive properties are at the origin of different kinds of multifunctional materials with unique characteristics. These solutions can form chiral nematic phases at rest, with tuneable photonic behavior, and exhibit a complex behavior associated with the onset
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Liquid crystalline cellulosic-based solutions described by distinctive properties are at the origin of different kinds of multifunctional materials with unique characteristics. These solutions can form chiral nematic phases at rest, with tuneable photonic behavior, and exhibit a complex behavior associated with the onset of a network of director field defects under shear. Techniques, such as Nuclear Magnetic Resonance (NMR), Rheology coupled with NMR (Rheo-NMR), rheology, optical methods, Magnetic Resonance Imaging (MRI), Wide Angle X-rays Scattering (WAXS), were extensively used to enlighten the liquid crystalline characteristics of these cellulosic solutions. Cellulosic films produced by shear casting and fibers by electrospinning, from these liquid crystalline solutions, have regained wider attention due to recognition of their innovative properties associated to their biocompatibility. Electrospun membranes composed by helical and spiral shape fibers allow the achievement of large surface areas, leading to the improvement of the performance of this kind of systems. The moisture response, light modulated, wettability and the capability of orienting protein and cellulose crystals, opened a wide range of new applications to the shear casted films. Characterization by NMR, X-rays, tensile tests, AFM, and optical methods allowed detailed characterization of those soft cellulosic materials. In this work, special attention will be given to recent developments, including, among others, a moisture driven cellulosic motor and electro-optical devices. Full article
(This article belongs to the Special Issue Liquid Crystals) Print Edition available
Open AccessReview Nanomaterial-Based Electrochemical Immunosensors for Clinically Significant Biomarkers
Materials 2014, 7(6), 4669-4709; doi:10.3390/ma7064669
Received: 31 March 2014 / Revised: 26 May 2014 / Accepted: 5 June 2014 / Published: 19 June 2014
Cited by 17 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text
Abstract
Nanotechnology has played a crucial role in the development of biosensors over the past decade. The development, testing, optimization, and validation of new biosensors has become a highly interdisciplinary effort involving experts in chemistry, biology, physics, engineering, and medicine. The sensitivity, the specificity
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Nanotechnology has played a crucial role in the development of biosensors over the past decade. The development, testing, optimization, and validation of new biosensors has become a highly interdisciplinary effort involving experts in chemistry, biology, physics, engineering, and medicine. The sensitivity, the specificity and the reproducibility of biosensors have improved tremendously as a result of incorporating nanomaterials in their design. In general, nanomaterials-based electrochemical immunosensors amplify the sensitivity by facilitating greater loading of the larger sensing surface with biorecognition molecules as well as improving the electrochemical properties of the transducer. The most common types of nanomaterials and their properties will be described. In addition, the utilization of nanomaterials in immunosensors for biomarker detection will be discussed since these biosensors have enormous potential for a myriad of clinical uses. Electrochemical immunosensors provide a specific and simple analytical alternative as evidenced by their brief analysis times, inexpensive instrumentation, lower assay cost as well as good portability and amenability to miniaturization. The role nanomaterials play in biosensors, their ability to improve detection capabilities in low concentration analytes yielding clinically useful data and their impact on other biosensor performance properties will be discussed. Finally, the most common types of electroanalytical detection methods will be briefly touched upon. Full article
(This article belongs to the Special Issue Advanced Nanomaterials for Biosensors)
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Open AccessCase Report Copper Tube Pitting in Santa Fe Municipal Water Caused by Microbial Induced Corrosion
Materials 2014, 7(6), 4321-4334; doi:10.3390/ma7064321
Received: 30 April 2014 / Revised: 16 May 2014 / Accepted: 20 May 2014 / Published: 5 June 2014
Cited by 4 | PDF Full-text (7395 KB) | HTML Full-text | XML Full-text
Abstract
Many copper water lines for municipal drinking water in Santa Fe, New Mexico USA, have developed pinhole leaks. The pitting matches the description of Type I pitting of copper, which has historically been attributed to water chemistry and to contaminants on the copper
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Many copper water lines for municipal drinking water in Santa Fe, New Mexico USA, have developed pinhole leaks. The pitting matches the description of Type I pitting of copper, which has historically been attributed to water chemistry and to contaminants on the copper tubing surface. However, more recent studies attribute copper pitting to microbial induced corrosion (MIC). In order to test for microbes, the copper tubing was fixed in hexamethyldisilazane (HMDS), then the tops of the corrosion mounds were broken open, and the interior of the corrosion pits were examined with scanning electron microscopy (SEM). The analysis found that microbes resembling actinobacteria were deep inside the pits and wedged between the crystallographic planes of the corroded copper grains. The presence of actinobacteria confirms the possibility that the cause of this pitting corrosion was MIC. This observation provides better understanding and new methods for preventing the pitting of copper tubing in municipal water. Full article
(This article belongs to the Special Issue Corrosion of Materials)
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