Materials

262 KiB

Open AccessArticle

Factors Affecting the Effectiveness of Inorganic Silicate Sealer Material through Multi-Quality Characteristics

by Si-Yu Zou, Ran Huang, Mao-Chieh Chi and Hui-Mi Hsu

Materials 2013, 6(3), 1191-1204; https://doi.org/10.3390/ma6031191 - 22 Mar 2013

Cited by 16 | Viewed by 5021

This study investigates the effectiveness of concrete protection with two inorganic silicate sealer materials (ISSMs). The Taguchi method and grey relational analysis (GRA) have been used to identify the key factors influencing concrete protection provided by the surface treatment. Seven control factors with [...] Read more.

This study investigates the effectiveness of concrete protection with two inorganic silicate sealer materials (ISSMs). The Taguchi method and grey relational analysis (GRA) have been used to identify the key factors influencing concrete protection provided by the surface treatment. Seven control factors with two levels were selected. By using the orthogonal array L₁₂ (2⁷), 12 experiments are chosen and four tests—the compressive strength test, resistivity test, absorption test and permeability test—were performed. Results have shown that the major factors affecting the protection effectiveness of ISSM are the water-binder ratio of mortar substrate, age of substrate for sealer application, addition of pozzolanic material and sealer type. Full article

(This article belongs to the Section Advanced Materials Characterization)

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6207 KiB

Open AccessReview

Polymeric Thin Films for Organic Electronics: Properties and Adaptive Structures

by Sebastiano Cataldo and Bruno Pignataro

Materials 2013, 6(3), 1159-1190; https://doi.org/10.3390/ma6031159 - 22 Mar 2013

Cited by 34 | Viewed by 9809

Abstract

This review deals with the correlation between morphology, structure and performance of organic electronic devices including thin film transistors and solar cells. In particular, we report on solution processed devices going into the role of the 3D supramolecular organization in determining their electronic [...] Read more.

This review deals with the correlation between morphology, structure and performance of organic electronic devices including thin film transistors and solar cells. In particular, we report on solution processed devices going into the role of the 3D supramolecular organization in determining their electronic properties. A selection of case studies from recent literature are reviewed, relying on solution methods for organic thin-film deposition which allow fine control of the supramolecular aggregation of polymers confined at surfaces in nanoscopic layers. A special focus is given to issues exploiting morphological structures stemming from the intrinsic polymeric dynamic adaptation under non-equilibrium conditions. Full article

(This article belongs to the Special Issue Conjugated Polymers 2012)

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Graphical abstract

2057 KiB

Open AccessReview

Applications of Carbon Nanotubes for Lithium Ion Battery Anodes

by Zhili Xiong, Young Soo Yun and Hyoung-Joon Jin

Materials 2013, 6(3), 1138-1158; https://doi.org/10.3390/ma6031138 - 21 Mar 2013

Cited by 166 | Viewed by 15270

Abstract

Carbon nanotubes (CNTs) have displayed great potential as anode materials for lithium ion batteries (LIBs) due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of CNT-based anodes are considerably improved compared to the conventional graphite-based anodes. Additionally, [...] Read more.

Carbon nanotubes (CNTs) have displayed great potential as anode materials for lithium ion batteries (LIBs) due to their unique structural, mechanical, and electrical properties. The measured reversible lithium ion capacities of CNT-based anodes are considerably improved compared to the conventional graphite-based anodes. Additionally, the opened structure and enriched chirality of CNTs can help to improve the capacity and electrical transport in CNT-based LIBs. Therefore, the modification of CNTs and design of CNT structure provide strategies for improving the performance of CNT-based anodes. CNTs could also be assembled into free-standing electrodes without any binder or current collector, which will lead to increased specific energy density for the overall battery design. In this review, we discuss the mechanism of lithium ion intercalation and diffusion in CNTs, and the influence of different structures and morphologies on their performance as anode materials for LIBs. Full article

(This article belongs to the Special Issue Carbon Nanotubes)

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2487 KiB

Open AccessArticle

Recent Advances in Creep Modelling of the Nickel Base Superalloy, Alloy 720Li

by William Harrison, Mark Whittaker and Steve Williams

Materials 2013, 6(3), 1118-1137; https://doi.org/10.3390/ma6031118 - 20 Mar 2013

Cited by 28 | Viewed by 8650

Abstract

Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, [...] Read more.

Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, particularly in extrapolation of short term results to long term predictions. In the aerospace industry however, long term creep behaviour is not critical and more focus is required on the prediction of times to specific creep strains. The current paper illustrates the capability of the Wilshire equations to recreate full creep curves in a modern nickel superalloy. Furthermore, a finite-element model based on this method has been shown to accurately predict stress relaxation behaviour allowing more accurate component lifing. Full article

(This article belongs to the Special Issue Superalloys)

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122 KiB

Open AccessArticle

Towards a Consensus View on Understanding Nanomaterials Hazards and Managing Exposure: Knowledge Gaps and Recommendations

by Geoffrey Hunt, Iseult Lynch, Flemming Cassee, Richard D. Handy, Teresa F. Fernandes, Markus Berges, Thomas A. J. Kuhlbusch, Maria Dusinska and Michael Riediker

Materials 2013, 6(3), 1090-1117; https://doi.org/10.3390/ma6031090 - 20 Mar 2013

Cited by 29 | Viewed by 8966

Abstract

The aim of this article is to present an overview of salient issues of exposure, characterisation and hazard assessment of nanomaterials as they emerged from the consensus-building of experts undertaken within the four year European Commission coordination project NanoImpactNet. The approach adopted is [...] Read more.

The aim of this article is to present an overview of salient issues of exposure, characterisation and hazard assessment of nanomaterials as they emerged from the consensus-building of experts undertaken within the four year European Commission coordination project NanoImpactNet. The approach adopted is to consolidate and condense the findings and problem-identification in such a way as to identify knowledge-gaps and generate a set of interim recommendations of use to industry, regulators, research bodies and funders. The categories of recommendation arising from the consensual view address: significant gaps in vital factual knowledge of exposure, characterisation and hazards; the development, dissemination and standardisation of appropriate laboratory protocols; address a wide range of technical issues in establishing an adequate risk assessment platform; the more efficient and coordinated gathering of basic data; greater inter-organisational cooperation; regulatory harmonization; the wider use of the life-cycle approaches; and the wider involvement of all stakeholders in the discussion and solution-finding efforts for nanosafety. Full article

(This article belongs to the Special Issue Nanotoxicology)

1782 KiB

Open AccessArticle

Thermo-Mechanical Behavior of Textile Heating Fabric Based on Silver Coated Polymeric Yarn

by Syed Talha Ali Hamdani, Prasad Potluri and Anura Fernando

Materials 2013, 6(3), 1072-1089; https://doi.org/10.3390/ma6031072 - 20 Mar 2013

Cited by 71 | Viewed by 11671

Abstract

This paper presents a study conducted on the thermo-mechanical properties of knitted structures, the methods of manufacture, effect of contact pressure at the structural binding points, on the degree of heating. The test results also present the level of heating produced as a [...] Read more.

This paper presents a study conducted on the thermo-mechanical properties of knitted structures, the methods of manufacture, effect of contact pressure at the structural binding points, on the degree of heating. The test results also present the level of heating produced as a function of the separation between the supply terminals. The study further investigates the rate of heating and cooling of the knitted structures. The work also presents the decay of heating properties of the yarn due to overheating. Thermal images were taken to study the heat distribution over the surface of the knitted fabric. A tensile tester having constant rate of extension was used to stretch the fabric. The behavior of temperature profile of stretched fabric was observed. A comparison of heat generation by plain, rib and interlock structures was studied. It was observed from the series of experiments that there is a minimum threshold force of contact at binding points of a knitted structure is required to pass the electricity. Once this force is achieved, stretching the fabric does not affect the amount of heat produced. Full article

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

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300 KiB

Open AccessArticle

Quinacridone-Diketopyrrolopyrrole-Based Polymers for Organic Field-Effect Transistors

by Masahiro Akita, Itaru Osaka and Kazuo Takimiya

Materials 2013, 6(3), 1061-1071; https://doi.org/10.3390/ma6031061 - 18 Mar 2013

Cited by 11 | Viewed by 8260

Abstract

Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. In [...] Read more.

Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. In this paper, semiconducting polymers based on well-known pigments, namely, quinacridone and diketopyrrolopyrrole, are synthesized and characterized. The π-stacking distances are found to be 3.5–3.8 Å, which is fairly narrow for semiconducting polymers, indicating that they possess strong intermolecular interactions. Interestingly, polymer orientation is influenced by the composition of alkyl side chains. While the edge-on orientation is observed when the linear alkyl groups are introduced for all the side chains, the face-on orientation is observed when the branched alkyl groups are introduced either in the quinacridone or diketopyrrolopyrrole unit. It is found that the electronic structure of the present polymers is mostly affected by that of the diketopyrrolopyrrole unit, as evidenced by the absorption spectra and computation. Although the field-effect mobility of the polymers is modest, i.e., in the order of 10⁻⁴–10⁻³ cm²/Vs, these findings could be important information for the development of semiconducting polymers. Full article

(This article belongs to the Special Issue Conjugated Polymers)

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561 KiB

Open AccessArticle

Photoluminescence Study of Gallium Nitride Thin Films Obtained by Infrared Close Space Vapor Transport

by Guillermo Santana, Osvaldo De Melo, Jorge Aguilar-Hernández, Rogelio Mendoza-Pérez, B. Marel Monroy, Adolfo Escamilla-Esquivel, Máximo López-López, Francisco De Moure, Luis A. Hernández and Gerardo Contreras-Puente

Materials 2013, 6(3), 1050-1060; https://doi.org/10.3390/ma6031050 - 15 Mar 2013

Cited by 44 | Viewed by 9055

Abstract

Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature [...] Read more.

Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature PL spectra of all the GaN films show near band-edge emission (NBE) and a broad blue and green luminescence (BL, GL), which can be seen with the naked eye in a bright room. The sample grown by infrared CSVT on the silicon substrate shows several emission peaks from 2.4 to 3.22 eV with a pronounced red shift with respect to the band gap energy. The sample grown on sapphire shows strong and broad ultraviolet emission peaks (UVL) centered at 3.19 eV and it exhibits a red shift of NBE. The PL spectrum of GaN films deposited on fused silica exhibited a unique and strong blue-green emission peak centered at 2.38 eV. The presence of yellow and green luminescence in all samples is related to native defects in the structure such as dislocations in GaN and/or the presence of amorphous phases. We analyze the material quality that can be obtained by CSVT-IR in vacuum, which is a high yield technique with simple equipment set-up, in terms of the PL results obtained in each case. Full article

(This article belongs to the Special Issue Luminescent Materials 2013)

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1325 KiB

Open AccessReview

Advanced Electrodes for High Power Li-ion Batteries

by Karim Zaghib, Alain Mauger, Henri Groult, John B. Goodenough and Christian M. Julien

Materials 2013, 6(3), 1028-1049; https://doi.org/10.3390/ma6031028 - 15 Mar 2013

Cited by 118 | Viewed by 14372

Abstract

While little success has been obtained over the past few years in attempts to increase the capacity of Li-ion batteries, significant improvement in the power density has been achieved, opening the route to new applications, from hybrid electric vehicles to high-power electronics and [...] Read more.

While little success has been obtained over the past few years in attempts to increase the capacity of Li-ion batteries, significant improvement in the power density has been achieved, opening the route to new applications, from hybrid electric vehicles to high-power electronics and regulation of the intermittency problem of electric energy supply on smart grids. This success has been achieved not only by decreasing the size of the active particles of the electrodes to few tens of nanometers, but also by surface modification and the synthesis of new multi-composite particles. It is the aim of this work to review the different approaches that have been successful to obtain Li-ion batteries with improved high-rate performance and to discuss how these results prefigure further improvement in the near future. Full article

(This article belongs to the Special Issue Advanced Materials for Lithium Ion Batteries)

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1273 KiB

Open AccessArticle

Graphene versus Multi-Walled Carbon Nanotubes for Electrochemical Glucose Biosensing

by Dan Zheng, Sandeep Kumar Vashist, Michal Marcin Dykas, Surajit Saha, Khalid Al-Rubeaan, Edmond Lam, John H.T. Luong and Fwu-Shan Sheu

Materials 2013, 6(3), 1011-1027; https://doi.org/10.3390/ma6031011 - 14 Mar 2013

Cited by 69 | Viewed by 11589

Abstract

: A simple procedure was developed for the fabrication of electrochemical glucose biosensors using glucose oxidase (GOx), with graphene or multi-walled carbon nanotubes (MWCNTs). Graphene and MWCNTs were dispersed in 0.25% 3-aminopropyltriethoxysilane (APTES) and drop cast on 1% KOH-pre-treated glassy carbon electrodes (GCEs). [...] Read more.

: A simple procedure was developed for the fabrication of electrochemical glucose biosensors using glucose oxidase (GOx), with graphene or multi-walled carbon nanotubes (MWCNTs). Graphene and MWCNTs were dispersed in 0.25% 3-aminopropyltriethoxysilane (APTES) and drop cast on 1% KOH-pre-treated glassy carbon electrodes (GCEs). The EDC (1-ethyl-(3-dimethylaminopropyl) carbodiimide)-activated GOx was then bound covalently on the graphene- or MWCNT-modified GCE. Both the graphene- and MWCNT-based biosensors detected the entire pathophysiological range of blood glucose in humans, 1.4–27.9 mM. However, the direct electron transfer (DET) between GOx and the modified GCE’s surface was only observed for the MWCNT-based biosensor. The MWCNT-based glucose biosensor also provided over a four-fold higher current signal than its graphene counterpart. Several interfering substances, including drug metabolites, provoked negligible interference at pathological levels for both the MWCNT- and graphene-based biosensors. However, the former was more prone to interfering substances and drug metabolites at extremely pathological concentrations than its graphene counterpart. Full article

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632 KiB

Open AccessArticle

Cosmetic Analysis Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI)

by Diogo Noin De Oliveira, Sabrina De Bona Sartor, Mônica Siqueira Ferreira and Rodrigo Ramos Catharino

Materials 2013, 6(3), 1000-1010; https://doi.org/10.3390/ma6031000 - 13 Mar 2013

Cited by 24 | Viewed by 8264

Abstract

A new “omic” platform—Cosmetomics—that proves to be extremely simple and effective in terms of sample preparation and readiness for data acquisition/interpretation is presented. This novel approach employing Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) for cosmetic analysis has proven to readily identify and [...] Read more.

A new “omic” platform—Cosmetomics—that proves to be extremely simple and effective in terms of sample preparation and readiness for data acquisition/interpretation is presented. This novel approach employing Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) for cosmetic analysis has proven to readily identify and quantify compounds of interest. It also allows full control of all the production phases, as well as of the final product, by integration of both analytical and statistical data. This work has focused on products of daily use, namely nail polish, lipsticks and eyeliners of multiple brands sold in the worldwide market. Full article

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

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2664 KiB

Open AccessArticle

Grafting of Amines on Ethanol-Extracted SBA-15 for CO₂Adsorption

by Yong Li, Nannan Sun, Lei Li, Ning Zhao, Fukui Xiao, Wei Wei, Yuhan Sun and Wei Huang

Materials 2013, 6(3), 981-999; https://doi.org/10.3390/ma6030981 - 12 Mar 2013

Cited by 62 | Viewed by 9897

Abstract

SBA-15 prepared via ethanol extraction for template removing was grafted with three kinds of amine precursors (mono-, di-, tri-aminosilanes) to synthesis new CO₂ adsorbents. The SBA-15 support and the obtained adsorbents were characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), N [...] Read more.

SBA-15 prepared via ethanol extraction for template removing was grafted with three kinds of amine precursors (mono-, di-, tri-aminosilanes) to synthesis new CO₂ adsorbents. The SBA-15 support and the obtained adsorbents were characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), N₂ adsorption/desorption, thermogravimetry (TG), elemental analysis, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that, except higher silanol density, the ethanol-extracted SBA-15 support possessed a more regular mesophase and thicker walls than traditionally calcined samples, leading to a good stability of the adsorbent under steam treatment. The adsorption capacity of different amine-grafted samples was found to be influenced by not only the surface amine density, but also their physiochemical properties. These observations provide important support for further studies of applying amine-grafted adsorbents in practical CO₂ capture process. Full article

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

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501 KiB

Open AccessArticle

Preparation of Amidoxime Polyacrylonitrile Chelating Nanofibers and Their Application for Adsorption of Metal Ions

by Fenglin Huang, Yunfei Xu, Shiqin Liao, Dawei Yang, You-Lo Hsieh and Qufu Wei

Materials 2013, 6(3), 969-980; https://doi.org/10.3390/ma6030969 - 11 Mar 2013

Cited by 142 | Viewed by 9552

Abstract

Polyacrylonitrile (PAN) nanofibers were prepared by electrospinning and they were modified with hydroxylamine to synthesize amidoxime polyacrylonitrile (AOPAN) chelating nanofibers, which were applied to adsorb copper and iron ions. The conversion of the nitrile group in PAN was calculated by the gravimetric method. [...] Read more.

Polyacrylonitrile (PAN) nanofibers were prepared by electrospinning and they were modified with hydroxylamine to synthesize amidoxime polyacrylonitrile (AOPAN) chelating nanofibers, which were applied to adsorb copper and iron ions. The conversion of the nitrile group in PAN was calculated by the gravimetric method. The structure and surface morphology of the AOPAN nanofiber were characterized by a Fourier transform infrared spectrometer (FT-IR) and a scanning electron microscope (SEM), respectively. The adsorption abilities of Cu²⁺ and Fe³⁺ ions onto the AOPAN nanofiber mats were evaluated. FT-IR spectra showed nitrile groups in the PAN were partly converted into amidoxime groups. SEM examination demonstrated that there were no serious cracks or sign of degradation on the surface of the PAN nanofibers after chemical modification. The adsorption capacities of both copper and iron ions onto the AOPAN nanofiber mats were higher than those into the raw PAN nanofiber mats. The adsorption data of Cu²⁺ and Fe³⁺ ions fitted particularly well with the Langmuir isotherm. The maximal adsorption capacities of Cu²⁺ and Fe³⁺ ions were 215.18 and 221.37 mg/g, respectively. Full article

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1741 KiB

Open AccessReview

A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel

by Ai Du, Bin Zhou, Zhihua Zhang and Jun Shen

Materials 2013, 6(3), 941-968; https://doi.org/10.3390/ma6030941 - 8 Mar 2013

Cited by 427 | Viewed by 29002

Abstract

The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, [...] Read more.

The ultrahighly nanoporous aerogel is recognized as a state of matter rather than as a functional material, because of its qualitative differences in bulk properties, transitional density and enthalpy between liquid and gas, and diverse chemical compositions. In this review, the characteristics, classification, history and preparation of the aerogel were introduced. More attention was paid to the sol-gel method for preparing different kinds of aerogels, given its important role on bridging the synthetic parameters with the properties. At last, preparation of a novel single-component aerogel, design of a composite aerogel and industrial application of the aerogel were regarded as the research tendency of the aerogel state in the near future. Full article

(This article belongs to the Special Issue Advances in Sol-gel Derived Materials)

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284 KiB

Open AccessArticle

Effects of Hydrolysed Whey Proteins on the Techno-Functional Characteristics of Whey Protein-Based Films

by Markus Schmid, Lesley-Virgina Hinz, Florian Wild and Klaus Noller

Materials 2013, 6(3), 927-940; https://doi.org/10.3390/ma6030927 - 7 Mar 2013

Cited by 45 | Viewed by 7338

Abstract

Pure whey protein isolate (WPI)-based cast films are very brittle due to its strong formation of protein cross-linking of disulphide bonding, hydrogen bonding as well as hydrophobic and electrostatic interactions. However, this strong cross-linking is the reason for its final barrier performance. To [...] Read more.

Pure whey protein isolate (WPI)-based cast films are very brittle due to its strong formation of protein cross-linking of disulphide bonding, hydrogen bonding as well as hydrophobic and electrostatic interactions. However, this strong cross-linking is the reason for its final barrier performance. To overcome film brittleness of whey protein layers, plasticisers like glycerol are used. It reduces intermolecular interactions, increases the mobility of polymer chains and thus film flexibility can be achieved. The objective of this study was to investigate the influence of hydrolysed whey protein isolate (WPI) in whey protein isolate-based cast films on their techno-functional properties. Due to the fact, that the addition of glycerol is necessary but at the same time increases the free volume in the film leading to higher oxygen and water vapour permeability, the glycerol concentration was kept constant. Cast films with different ratios of hydrolysed and not hydrolysed WPI were produced. They were characterised in order to determine the influence of the lower molecular weight caused by the addition of hydrolysed WPI on the techno-functional properties. This study showed that increasing hydrolysed WPI concentrations significantly change the mechanical properties while maintaining the oxygen and water vapour permeability. The tensile and elastic film properties decreased significantly by reducing the average molecular weight whereas the yellowish coloration and the surface tension considerably increased. This study provided new data which put researchers and material developers in a position to tailor the characteristics of whey protein based films according to their intended application and further processing. Full article

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Open AccessArticle

Covalently Bonded Chitosan on Graphene Oxide via Redox Reaction

by Karina Bustos-Ramírez, Ana L. Martínez-Hernández, Gonzalo Martínez-Barrera, Miguel De Icaza, Víctor M. Castaño and Carlos Velasco-Santos

Materials 2013, 6(3), 911-926; https://doi.org/10.3390/ma6030911 - 7 Mar 2013

Cited by 95 | Viewed by 11136

Abstract

Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. [...] Read more.

Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. In this sense carbohydrates such as chitosan are extremely valuable because their functional groups play an important role in diversifying the applications of carbon nanomaterials. This paper reports the covalent attachment of chitosan onto graphene oxide, taking advantage of this carbohydrate at the nanometric level. Grafting is an innovative route to modify properties of graphene, a two-dimensional nanometric arrangement, which is one of the most novel and promising nanostructures. Chitosan grafting was achieved by redox reaction using different temperature conditions that impact on the morphology and features of graphene oxide sheets. Transmission Electron Microscopy, Fourier Transform Infrared, Raman and Energy Dispersive spectroscopies were used to study the surface of chitosan-grafted-graphene oxide. Results show a successful modification indicated by the functional groups found in the grafted material. Dispersions of chitosan-grafted-graphene oxide samples in water and hexane revealed different behavior due to the chemical groups attached to the graphene oxide sheet. Full article

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

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289 KiB

Open AccessArticle

Ultrafast Transient Spectroscopy of Polymer/Fullerene Blends for Organic Photovoltaic Applications

by Sanjeev Singh and Zeev Valy Vardeny

Materials 2013, 6(3), 897-910; https://doi.org/10.3390/ma6030897 - 6 Mar 2013

Cited by 18 | Viewed by 6698

Abstract

We measured the picoseconds (ps) transient dynamics of photoexcitations in blends of regio-regular poly(3-hexyl-thiophene) (RR-P3HT) (donors-D) and fullerene (PCBM) (acceptor-A) in an unprecedented broad spectral range of 0.25 to 2.5 eV. In D-A blends with maximum domain separation, such as RR-P3HT/PCBM, with (1.2:1) [...] Read more.

We measured the picoseconds (ps) transient dynamics of photoexcitations in blends of regio-regular poly(3-hexyl-thiophene) (RR-P3HT) (donors-D) and fullerene (PCBM) (acceptor-A) in an unprecedented broad spectral range of 0.25 to 2.5 eV. In D-A blends with maximum domain separation, such as RR-P3HT/PCBM, with (1.2:1) weight ratio having solar cell power conversion efficiency of ~4%, we found that although the intrachain excitons in the polymer domains decay within ~10 ps, no charge polarons are generated at their expense up to ~1 ns. Instead, there is a build-up of charge-transfer (CT) excitons at the D-A interfaces having the same kinetics as the exciton decay. The CT excitons dissociate into separate polarons in the D and A domains at a later time (>1 ns). This “two-step” charge photogeneration process may be typical in organic bulk heterojunction cells. We also report the effect of adding spin 1/2 radicals, Galvinoxyl on the ultrafast photoexcitation dynamics in annealed films of RR-P3HT/PCBM blend. The addition of Galvinoxyl radicals to the blend reduces the geminate recombination rate of photogenerated CT excitons. In addition, the photoexcitation dynamics in a new D-A blend of RR-P3HT/Indene C60 trisadduct (ICTA) has been studied and compared with the dynamics in RR-P3HT/PCBM. Full article

(This article belongs to the Special Issue Photovoltaic Materials)

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448 KiB

Open AccessArticle

Electronic Two-Transition-Induced Enhancement of Emission Efficiency in Polymer Light-Emitting Diodes

by Ren-Ai Chen, Cong Wang, Sheng Li and Thomas F. George

Materials 2013, 6(3), 886-896; https://doi.org/10.3390/ma6030886 - 6 Mar 2013

Viewed by 5229

Abstract

With the development of experimental techniques, effective injection and transportation of electrons is proven as a way to obtain polymer light-emitting diodes (PLEDs) with high quantum efficiency. This paper reveals a valid mechanism for the enhancement of quantum efficiency in PLEDs. When an [...] Read more.

With the development of experimental techniques, effective injection and transportation of electrons is proven as a way to obtain polymer light-emitting diodes (PLEDs) with high quantum efficiency. This paper reveals a valid mechanism for the enhancement of quantum efficiency in PLEDs. When an external electric field is applied, the interaction between a negative polaron and triplet exciton leads to an electronic two-transition process, which induces the exciton to emit light and thus improve the emission efficiency of PLEDs. Full article

(This article belongs to the Special Issue Conjugated Polymers 2012)

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Open AccessArticle

An Efficient Local Molecular Dynamics Polymerization Simulation Combined with an Ab Initio MO Method

by Peng Xie, Yuuichi Orimoto and Yuriko Aoki

Materials 2013, 6(3), 870-885; https://doi.org/10.3390/ma6030870 - 6 Mar 2013

Cited by 7 | Viewed by 7606

Abstract

A new local ab initio molecular dynamics method, namely elongation molecular dynamics (ELG-MD) is proposed for highly efficient simulations of aperiodic polymer systems. ELG-MD combines the elongation method (ELG) with the Gear predictor corrector (GPC) algorithm of molecular dynamics simulation. In this method, [...] Read more.

A new local ab initio molecular dynamics method, namely elongation molecular dynamics (ELG-MD) is proposed for highly efficient simulations of aperiodic polymer systems. ELG-MD combines the elongation method (ELG) with the Gear predictor corrector (GPC) algorithm of molecular dynamics simulation. In this method, the local gradients acting on the atom’s nucleus in the active region are calculated by the ELG method while the equations of the nucleus’s motion are solved by the GPC algorithm. In this work, the first application of this ELG-MD method is described to investigate the stable conformation of polyglycine with surrounding water molecules. The water effects on the structure of polyglycine are examined. The ELG-MD simulations show that the formation of the polyglycine helix is strongly induced by the hydrogen bonds observed in two types of H-bond rings. Full article

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937 KiB

Open AccessArticle

From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

by Diego Manfredi, Flaviana Calignano, Manickavasagam Krishnan, Riccardo Canali, Elisa Paola Ambrosio and Eleonora Atzeni

Materials 2013, 6(3), 856-869; https://doi.org/10.3390/ma6030856 - 6 Mar 2013

Cited by 288 | Viewed by 17050

Abstract

In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of [...] Read more.

In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed. Full article

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2290 KiB

Open AccessArticle

Multifunctional Cement Composites Strain and Damage Sensors Applied on Reinforced Concrete (RC) Structural Elements

by Francisco Javier Baeza, Oscar Galao, Emilio Zornoza and Pedro Garcés

Materials 2013, 6(3), 841-855; https://doi.org/10.3390/ma6030841 - 6 Mar 2013

Cited by 149 | Viewed by 9229

Abstract

In this research, strain-sensing and damage-sensing functional properties of cement composites have been studied on a conventional reinforced concrete (RC) beam. Carbon nanofiber (CNFCC) and fiber (CFCC) cement composites were used as sensors on a 4 m long RC beam. Different casting conditions [...] Read more.

In this research, strain-sensing and damage-sensing functional properties of cement composites have been studied on a conventional reinforced concrete (RC) beam. Carbon nanofiber (CNFCC) and fiber (CFCC) cement composites were used as sensors on a 4 m long RC beam. Different casting conditions (in situ or attached), service location (under tension or compression) and electrical contacts (embedded or superficial) were compared. Both CNFCC and CFCC were suitable as strain sensors in reversible (elastic) sensing condition testing. CNFCC showed higher sensitivities (gage factor up to 191.8), while CFCC only reached gage factors values of 178.9 (tension) or 49.5 (compression). Furthermore, damage-sensing tests were run, increasing the applied load progressively up to the RC beam failure. In these conditions, CNFCC sensors were also strain sensitive, but no damage sensing mechanism was detected for the strain levels achieved during the tests. Hence, these cement composites could act as strain sensors, even for severe damaged structures near to their collapse. Full article

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

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304 KiB

Open AccessReview

Dye Sensitizers for Photodynamic Therapy

by Alexandra B. Ormond and Harold S. Freeman

Materials 2013, 6(3), 817-840; https://doi.org/10.3390/ma6030817 - 6 Mar 2013

Cited by 714 | Viewed by 24231

Abstract

Photofrin^® was first approved in the 1990s as a sensitizer for use in treating cancer via photodynamic therapy (PDT). Since then a wide variety of dye sensitizers have been developed and a few have been approved for PDT treatment of skin and [...] Read more.

Photofrin^® was first approved in the 1990s as a sensitizer for use in treating cancer via photodynamic therapy (PDT). Since then a wide variety of dye sensitizers have been developed and a few have been approved for PDT treatment of skin and organ cancers and skin diseases such as acne vulgaris. Porphyrinoid derivatives and precursors have been the most successful in producing requisite singlet oxygen, with Photofrin^® still remaining the most efficient sensitizer (quantum yield = 0.89) and having broad food and drug administration (FDA) approval for treatment of multiple cancer types. Other porphyrinoid compounds that have received approval from US FDA and regulatory authorities in other countries include benzoporphyrin derivative monoacid ring A (BPD-MA), meta-tetra(hydroxyphenyl)chlorin (m-THPC), N-aspartyl chlorin e6 (NPe6), and precursors to endogenous protoporphyrin IX (PpIX): 1,5-aminolevulinic acid (ALA), methyl aminolevulinate (MAL), hexaminolevulinate (HAL). Although no non-porphyrin sensitizer has been approved for PDT applications, a small number of anthraquinone, phenothiazine, xanthene, cyanine, and curcuminoid sensitizers are under consideration and some are being evaluated in clinical trials. This review focuses on the nature of PDT, dye sensitizers that have been approved for use in PDT, and compounds that have entered or completed clinical trials as PDT sensitizers. Full article

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

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Open AccessArticle

Characterization and Stability of Tanshinone IIA Solid Dispersions with Hydroxyapatite

by Xiaopan Wang, Li Li, Wei Huo, Lulu Hou, Zhiying Zhao and Weiguang Li

Materials 2013, 6(3), 805-816; https://doi.org/10.3390/ma6030805 - 6 Mar 2013

Cited by 21 | Viewed by 5947

Abstract

Solid dispersions of tanshinone IIA (TanIIA) using hydroxyapatite (HAp) as the dispersing carrier (TanIIA-HAp SDs) were prepared by the solvent evaporation method. The formed solid dispersions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry analysis (DSC), X-ray powder diffraction (XRPD) and [...] Read more.

Solid dispersions of tanshinone IIA (TanIIA) using hydroxyapatite (HAp) as the dispersing carrier (TanIIA-HAp SDs) were prepared by the solvent evaporation method. The formed solid dispersions were characterized by scanning electron microscopy (SEM), differential scanning calorimetry analysis (DSC), X-ray powder diffraction (XRPD) and Fourier transforms infrared (FTIR) spectroscopy. The in vitro dissolution rate and the stability of TanIIA-HAp SDs were also evaluated. DSC and XRPD showed that TanIIA was changed from a crystalline to an amorphous form. FTIR suggested the presence of interactions between TanIIA and HAp in solid dispersions. The result of an in vitro dissolution study showed that the dissolution rate of TanIIA-HAp SDs was nearly 7.11-folds faster than free TanIIA. Data from stability studies for over one year of TanIIA-HAp SDs performed under room temperature revealed no significant differences in drug content and dissolution behavior. All these results indicated that HAp may be a promising carrier for improving the oral absorption of TanIIA. Full article

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Open AccessArticle

Influence of N₂ Partial Pressure on Structure and Mechanical Properties of TiAlN/Al₂O₃ Multilayers

by Jingyue Yan, Lei Dong, Chongkuan Gao, Ning Wang and Dejun Li

Materials 2013, 6(3), 795-804; https://doi.org/10.3390/ma6030795 - 28 Feb 2013

Cited by 5 | Viewed by 5781

Abstract

TiAlN/Al₂O₃multilayers with different Ar/N₂ ratios were deposited on Sisubstrates in different N₂ partial pressure by magnetron sputtering. The crystalline and multilayer structures of the multilayers were determined by a glancing angle X-ray diffractometer (XRD). A nanoindenter [...] Read more.

TiAlN/Al₂O₃multilayers with different Ar/N₂ ratios were deposited on Sisubstrates in different N₂ partial pressure by magnetron sputtering. The crystalline and multilayer structures of the multilayers were determined by a glancing angle X-ray diffractometer (XRD). A nanoindenter was used to evaluate the hardness, the elastic modulus and scratch scan of the multilayers. The chemical bonding was investigated by a X-ray Photoelectron Spectroscopy (XPS). The maximum hardness (36.3 GPa) and elastic modulus (466 GPa) of the multilayers was obtained when Ar/N₂ ratio was 18:1. The TiAlN/Al₂O₃ multilayers were crystallized with orientation in the (111) and (311) crystallographic planes. The multilayers displayed stably plastic recovery in different Ar/N₂ ratios. The scratch scan and post scan surface profiles of TiAlN/Al₂O₃ multilayers showed the highest critical fracture load (L_c) of 53 mN for the multilayer of Ar/N₂ = 18:1. It indicated that the multilayer had better practical adhesion strength and fracture resistance. Full article

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

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Open AccessArticle

Biosynthesis and Characterization of Nanocellulose-Gelatin Films

by Siriporn Taokaew, Sutasinee Seetabhawang, Pongpun Siripong and Muenduen Phisalaphong

Materials 2013, 6(3), 782-794; https://doi.org/10.3390/ma6030782 - 28 Feb 2013

Cited by 99 | Viewed by 10943

Abstract

A nanocellulose-gelatin (bacterial cellulose gelatin (BCG)) film was developed by a supplement of gelatin, at a concentration of 1%–10% w/v, in a coconut-water medium under the static cultivation of Acetobacter xylinum. The two polymers exhibited a certain degree of miscibility. The BCG [...] Read more.

A nanocellulose-gelatin (bacterial cellulose gelatin (BCG)) film was developed by a supplement of gelatin, at a concentration of 1%–10% w/v, in a coconut-water medium under the static cultivation of Acetobacter xylinum. The two polymers exhibited a certain degree of miscibility. The BCG film displayed dense and uniform homogeneous structures. The Fourier transform infrared spectroscopy (FTIR) results demonstrated interactions between the cellulose and gelatin. Incorporation of gelatin into a cellulose nanofiber network resulted in significantly improved optical transparency and water absorption capacity of the films. A significant drop in the mechanical strengths and a decrease in the porosity of the film were observed when the supplement of gelatin was more than 3% (w/v). The BCG films showed no cytotoxicity against Vero cells. Full article

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

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Open AccessReview

“Smart” Materials Based on Cellulose: A Review of the Preparations, Properties, and Applications

by Xiaoyun Qiu and Shuwen Hu

Materials 2013, 6(3), 738-781; https://doi.org/10.3390/ma6030738 - 28 Feb 2013

Cited by 430 | Viewed by 28575

Abstract

Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, hydrophilicity, biocompatibility, and biodegradability. Thus, cellulose has been widely applied in many fields. “Smart” materials based on cellulose have great advantages—especially their intelligent behaviors in [...] Read more.

Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, hydrophilicity, biocompatibility, and biodegradability. Thus, cellulose has been widely applied in many fields. “Smart” materials based on cellulose have great advantages—especially their intelligent behaviors in reaction to environmental stimuli—and they can be applied to many circumstances, especially as biomaterials. This review aims to present the developments of “smart” materials based on cellulose in the last decade, including the preparations, properties, and applications of these materials. The preparations of “smart” materials based on cellulose by chemical modifications and physical incorporating/blending were reviewed. The responsiveness to pH, temperature, light, electricity, magnetic fields, and mechanical forces, etc. of these “smart” materials in their different forms such as copolymers, nanoparticles, gels, and membranes were also reviewed, and the applications as drug delivery systems, hydrogels, electronic active papers, sensors, shape memory materials and smart membranes, etc. were also described in this review. Full article

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

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264 KiB

Open AccessArticle

Behavior of Elastoplastic Auxetic Microstructural Arrays

by Rivka Gilat and Jacob Aboudi

Materials 2013, 6(3), 726-737; https://doi.org/10.3390/ma6030726 - 28 Feb 2013

Cited by 14 | Viewed by 5628

Abstract

A continuum-based micromechanical model is employed for the prediction of the elasto-plastic behavior of periodic microstructural arrays that can generate negative values of Poisson’s ratios. The combined effects of the negative Poisson’s ratio generated by the array microstructure and the elastoplastic behavior of [...] Read more.

A continuum-based micromechanical model is employed for the prediction of the elasto-plastic behavior of periodic microstructural arrays that can generate negative values of Poisson’s ratios. The combined effects of the negative Poisson’s ratio generated by the array microstructure and the elastoplastic behavior of the constituents are studied. A design methodology for the determination of the constituents’ properties of two-phase arrays that generate required values of negative Poisson’s ratio is considered. Full article

(This article belongs to the Special Issue Auxetic Materials)

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443 KiB

Open AccessArticle

Structural and Luminescence Properties of Lu₂O₃:Eu³⁺ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

by Angel De Jesus Morales Ramírez, Margarita García Hernández, Antonieta García Murillo, Felipe De Jesús Carrillo Romo, Joel Moreno Palmerin, Dulce Yolotzin Medina Velazquez and María Luz Carrera Jota

Materials 2013, 6(3), 713-725; https://doi.org/10.3390/ma6030713 - 26 Feb 2013

Cited by 6 | Viewed by 6851

Abstract

Lu₂O₃:Eu³⁺ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were [...] Read more.

Lu₂O₃:Eu³⁺ transparent, high density, and optical quality thin films were prepared using the sol-gel dip-coating technique, starting with lutetium and europium nitrates as precursors and followed by hydrolysis in an ethanol-ethylene glycol solution. Acetic acid and acetylacetonate were incorporated in order to adjust pH and as a sol stabilizer. In order to increment the thickness of the films and orient the structure, F127 Pluronic acid was incorporated during the sol formation. Structural, morphological, and optical properties of the films were investigated for different F127/Lu molar ratios (0–5) in order to obtain high optical quality films with enhanced thickness compared with the traditional method. X-ray diffraction (XRD) shows that the films present a highly oriented cubic structure <111> beyond 1073 K for a 3-layer film, on silica glass substrates. The thickness, density, porosity, and refractive index evolution of the films were investigated by means of m-lines microscopy along with the morphology by scanning electron microscope (SEM) and luminescent properties. Full article

(This article belongs to the Special Issue Advances in Sol-gel Derived Materials)

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Materials, Volume 6, Issue 3 (March 2013) – 28 articles , Pages 713-1204

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