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Materials, Volume 8, Issue 7 (July 2015) , Pages 3793-4630

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Open AccessArticle Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope
Materials 2015, 8(7), 4618-4630; https://doi.org/10.3390/ma8074618
Received: 27 May 2015 / Revised: 6 July 2015 / Accepted: 16 July 2015 / Published: 22 July 2015
Cited by 1 | Viewed by 1768 | PDF Full-text (2262 KB) | HTML Full-text | XML Full-text
Abstract
The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr [...] Read more.
The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. Full article
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Open AccessCommunication Sonodelivery Facilitates Sustained Luciferase Expression from an Episomal Vector in Skeletal Muscle
Materials 2015, 8(7), 4608-4617; https://doi.org/10.3390/ma8074608
Received: 12 May 2015 / Revised: 13 July 2015 / Accepted: 15 July 2015 / Published: 22 July 2015
Cited by 2 | Viewed by 1704 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text
Abstract
Successful gene delivery to skeletal muscle is a desirable goal, not only for treating muscle diseases, but also for immunization, treatment of metabolic disorders, and/or delivering gene expression that can treat systemic conditions, such as bone metastatic cancer, for example. Although naked DNA [...] Read more.
Successful gene delivery to skeletal muscle is a desirable goal, not only for treating muscle diseases, but also for immunization, treatment of metabolic disorders, and/or delivering gene expression that can treat systemic conditions, such as bone metastatic cancer, for example. Although naked DNA uptake into skeletal muscle is possible, it is largely inefficient in the absence of additional chemical or physical delivery methods. We describe a system for delivery of non-viral or plasmid DNA to skeletal muscle using ultrasound-assisted sonoporation of a nanoplex combining plasmid DNA and a branched polymer based on poly(cyclooctene-graft-oligopeptide). The materials and methods described herein promise to advance the field of sonodelivery and of gene delivery to muscle for therapeutic applications since a simple system is presented that enables long-term gene expression in vivo with the promise of a minimal inflammatory gene expression profile. Full article
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Open AccessArticle Engineering of Iron-Based Magnetic Activated Carbon Fabrics for Environmental Remediation
Materials 2015, 8(7), 4593-4607; https://doi.org/10.3390/ma8074593
Received: 4 June 2015 / Revised: 30 June 2015 / Accepted: 10 July 2015 / Published: 22 July 2015
Cited by 14 | Viewed by 1955 | PDF Full-text (2285 KB) | HTML Full-text | XML Full-text
Abstract
Magnetic Fe3O4, Fe and Fe/Pd nanoparticles embedded within the pores of activated carbon fabrics (ACF) were prepared by impregnation of the ACF in iron acetylacetanoate (Fe(acac)3) ethanol solution, followed by thermal decomposition of the embedded iron precursor [...] Read more.
Magnetic Fe3O4, Fe and Fe/Pd nanoparticles embedded within the pores of activated carbon fabrics (ACF) were prepared by impregnation of the ACF in iron acetylacetanoate (Fe(acac)3) ethanol solution, followed by thermal decomposition of the embedded iron precursor at 200, 400 and 600 °C in an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area, pore volume, and magnetic properties of the various functionalized ACF was elucidated. The Fe nanoparticles within the ACF were also doped with tinier Pd nanoparticles, by impregnation of the Fe/ACF in palladium acetate ethanol solution. The potential use of the functionalized ACF for removal of a model azo-dye, orange II, was demonstrated. This study illustrated the enhanced removal of the dye from an aqueous solution according to the following order: Fe/Pd/ACF > Fe/ACF > ACF. In addition, the enhanced activity of Fe3O4/ACF in the presence of increasing concentrations of H2O2 (Fenton catalysts) was also illustrated. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Development and Assessment of a New Empirical Model for Predicting Full Creep Curves
Materials 2015, 8(7), 4582-4592; https://doi.org/10.3390/ma8074582
Received: 8 June 2015 / Revised: 6 July 2015 / Accepted: 9 July 2015 / Published: 22 July 2015
Cited by 2 | Viewed by 1708 | PDF Full-text (995 KB) | HTML Full-text | XML Full-text
Abstract
This paper details the development and assessment of a new empirical creep model that belongs to the limited ranks of models reproducing full creep curves. The important features of the model are that it is fully standardised and is universally applicable. By standardising, [...] Read more.
This paper details the development and assessment of a new empirical creep model that belongs to the limited ranks of models reproducing full creep curves. The important features of the model are that it is fully standardised and is universally applicable. By standardising, the user no longer chooses functions but rather fits one set of constants only. Testing it on 7 contrasting materials, reproducing 181 creep curves we demonstrate its universality. New model and Theta Projection curves are compared to one another using an assessment tool developed within this paper. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
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Open AccessReview Current Approach in Surface Plasmons for Thin Film and Wire Array Solar Cell Applications
Materials 2015, 8(7), 4565-4581; https://doi.org/10.3390/ma8074565
Received: 30 April 2015 / Revised: 1 July 2015 / Accepted: 14 July 2015 / Published: 22 July 2015
Cited by 6 | Viewed by 2266 | PDF Full-text (1733 KB) | HTML Full-text | XML Full-text
Abstract
Surface plasmons, which exist along the interface of a metal and a dielectric, have been proposed as an efficient alternative method for light trapping in solar cells during the past ten years. With unique properties such as superior light scattering, optical trapping, guide [...] Read more.
Surface plasmons, which exist along the interface of a metal and a dielectric, have been proposed as an efficient alternative method for light trapping in solar cells during the past ten years. With unique properties such as superior light scattering, optical trapping, guide mode coupling, near field concentration, and hot-electron generation, metallic nanoparticles or nanostructures can be tailored to a certain geometric design to enhance solar cell conversion efficiency and to reduce the material costs. In this article, we review current approaches on different kinds of solar cells, such as crystalline silicon (c-Si) and amorphous silicon (a-Si) thin film solar cells, organic solar cells, nanowire array solar cells, and single nanowire solar cells. Full article
(This article belongs to the Special Issue Plasmonic Materials)
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Open AccessArticle Thermal Stability and Magnetic Properties of Polyvinylidene Fluoride/Magnetite Nanocomposites
Materials 2015, 8(7), 4553-4564; https://doi.org/10.3390/ma8074553
Received: 29 May 2015 / Revised: 11 June 2015 / Accepted: 10 July 2015 / Published: 22 July 2015
Cited by 10 | Viewed by 1578 | PDF Full-text (1421 KB) | HTML Full-text | XML Full-text | Correction
Abstract
This work describes the thermal stability and magnetic properties of polyvinylidene fluoride (PVDF)/magnetite nanocomposites fabricated using the solution mixing technique. The image of transmission electron microscopy for PVDF/magnetite nanocomposites reveals that the 13 nm magnetite nanoparticles are well distributed in PVDF matrix. The [...] Read more.
This work describes the thermal stability and magnetic properties of polyvinylidene fluoride (PVDF)/magnetite nanocomposites fabricated using the solution mixing technique. The image of transmission electron microscopy for PVDF/magnetite nanocomposites reveals that the 13 nm magnetite nanoparticles are well distributed in PVDF matrix. The electroactive β-phase and piezoelectric responses of PVDF/magnetite nanocomposites are increased as the loading of magnetite nanoparticles increases. The piezoelectric responses of PVDF/magnetite films are extensively increased about five times in magnitude with applied strength of electrical field at 35 MV/m. The magnetic properties of PVDF/magnetite nanocomposites exhibit supermagnetism with saturation magnetization in the range of 1.6 × 10−3–3.1 × 10−3 emu/g, which increases as the amount of magnetite nanoparticles increases. The incorporation of 2 wt % magnetite nanoparticles into the PVDF matrix improves the thermal stability about 25 °C as compared to that of PVDF. The effect of magnetite particles on the isothermal degradation behavior of PVDF is also investigated. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Towards InAs/InGaAs/GaAs Quantum Dot Solar Cells Directly Grown on Si Substrate
Materials 2015, 8(7), 4544-4552; https://doi.org/10.3390/ma8074544
Received: 18 June 2015 / Revised: 12 July 2015 / Accepted: 14 July 2015 / Published: 22 July 2015
Cited by 3 | Viewed by 2201 | PDF Full-text (796 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports on an initial assessment of the direct growth of In(Ga)As/GaAs quantum dots (QDs) solar cells on nanostructured surface Si substrate by molecular beam epitaxy (MBE). The effect of inserting 40 InAs/InGaAs/GaAs QDs layers in the intrinsic region of the heterojunction [...] Read more.
This paper reports on an initial assessment of the direct growth of In(Ga)As/GaAs quantum dots (QDs) solar cells on nanostructured surface Si substrate by molecular beam epitaxy (MBE). The effect of inserting 40 InAs/InGaAs/GaAs QDs layers in the intrinsic region of the heterojunction pin-GaAs/n+-Si was evaluated using photocurrent spectroscopy in comparison with pin-GaAs/n+-Si and pin-GaAs/GaAs without QDs. The results reveal the clear contribution of the QDs layers to the improvement of the spectral response up to 1200 nm. The novel structure has been studied by X ray diffraction (XRD), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). These results provide considerable insights into low cost III-V material-based solar cells. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices) Printed Edition available
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Open AccessArticle Notched Long-Period Fiber Grating with an Amine-Modified Surface Nanostructure for Carbon Dioxide Gas Sensing
Materials 2015, 8(7), 4535-4543; https://doi.org/10.3390/ma8074535
Received: 29 May 2015 / Revised: 29 May 2015 / Accepted: 16 July 2015 / Published: 21 July 2015
Cited by 4 | Viewed by 1804 | PDF Full-text (1554 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the fabrication and application of a notched long-period fiber grating (NLPFG) with an amine-modified surface nanostructure for carbon dioxide (CO2) gas sensing. The NLPFG with the modified surface nanostructure was fabricated by using inductively coupled plasma (ICP) etching [...] Read more.
This paper presents the fabrication and application of a notched long-period fiber grating (NLPFG) with an amine-modified surface nanostructure for carbon dioxide (CO2) gas sensing. The NLPFG with the modified surface nanostructure was fabricated by using inductively coupled plasma (ICP) etching with an Ag nanoparticle etching barrier. The experimental results show that the spectra were changed with the CO2 gas flow within 12 min. Thereafter, the spectra of the NLPFG remained steady and unchanged. During the absorption process, the transmission loss was decreased by approximately 2.019 dB, and the decreased rate of transmission loss was 0.163 dB/min. The sensitivity was about −0.089 dB/%. These results demonstrate that the NLPFG CO2 gas sensor has the advantages of steady performance, repeatability, and low cost. Therefore, the NLPFG can be utilized as a reliable CO2 gas sensor. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
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Open AccessReview Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane
Materials 2015, 8(7), 4512-4534; https://doi.org/10.3390/ma8074512
Received: 6 May 2015 / Revised: 6 May 2015 / Accepted: 15 July 2015 / Published: 21 July 2015
Cited by 11 | Viewed by 2044 | PDF Full-text (1668 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of [...] Read more.
Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane. Full article
(This article belongs to the Special Issue Hydrogen Storage Materials)
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Open AccessEditorial Mechanics of Biological Tissues and Biomaterials: Current Trends
Materials 2015, 8(7), 4505-4511; https://doi.org/10.3390/ma8074505
Received: 3 July 2015 / Revised: 3 July 2015 / Accepted: 17 July 2015 / Published: 21 July 2015
Cited by 2 | Viewed by 1648 | PDF Full-text (332 KB) | HTML Full-text | XML Full-text
Abstract
Investigation of the mechanical behavior of biological tissues and biomaterials has been an active area of research for several decades. However, in recent years, the enthusiasm in understanding the mechanical behavior of biological tissues and biomaterials has increased significantly due to the development [...] Read more.
Investigation of the mechanical behavior of biological tissues and biomaterials has been an active area of research for several decades. However, in recent years, the enthusiasm in understanding the mechanical behavior of biological tissues and biomaterials has increased significantly due to the development of novel biomaterials for new fields of application, along with the emergence of advanced computational techniques. The current Special Issue is a collection of studies that address various topics within the general theme of “mechanics of biomaterials”. This editorial aims to present the context within which the studies of this Special Issue could be better understood. I, therefore, try to identify some of the most important research trends in the study of the mechanical behavior of biological tissues and biomaterials. Full article
(This article belongs to the Special Issue Mechanics of Biomaterials) Printed Edition available
Open AccessArticle Human Dental Pulp Cells Responses to Apatite Precipitation from Dicalcium Silicates
Materials 2015, 8(7), 4491-4504; https://doi.org/10.3390/ma8074491
Received: 2 June 2015 / Revised: 8 July 2015 / Accepted: 15 July 2015 / Published: 20 July 2015
Cited by 17 | Viewed by 1750 | PDF Full-text (2478 KB) | HTML Full-text | XML Full-text
Abstract
Unraveling the mechanisms behind the processes of cell attachment and the enhanced proliferation that occurs as a response to the presence of calcium silicate-based materials needs to be better understood so as to expand the applications of silicate-based materials. Ions in the environment [...] Read more.
Unraveling the mechanisms behind the processes of cell attachment and the enhanced proliferation that occurs as a response to the presence of calcium silicate-based materials needs to be better understood so as to expand the applications of silicate-based materials. Ions in the environment may influence apatite precipitation and affect silicate ion release from silicate-based materials. Thus, the involvement of apatite precipitate in the regulation of cell behavior of human dental pulp cells (hDPCs) is also investigated in the present study, along with an investigation of the specific role of cell morphology and osteocalcin protein expression cultured on calcium silicate (CS) with different Dulbecco’s modified Eagle’s medium (DMEM). The microstructure and component of CS cement immersion in DMEM and P-free DMEM are analyzed. In addition, when hDPCs are cultured on CS with two DMEMs, we evaluate fibronectin (FN) and collagen type I (COL) secretion during the cell attachment stage. The facilitation of cell adhesion on CS has been confirmed and observed both by scanning with an electron microscope and using immunofluorescence imaging. The results indicate that CS is completely covered by an apatite layer with tiny spherical shapes on the surface in the DMEM, but not in the P-free DMEM. Compared to the P-free DMEM, the lower Ca ion in the DMEM may be attributed to the formation of the apatite on the surfaces of specimens as a result of consumption of the Ca ion from the DMEM. Similarly, the lower Si ion in the CS-soaked DMEM is attributed to the shielding effect of the apatite layer. The P-free DMEM group releases more Si ion increased COL and FN secretion, which promotes cell attachment more effectively than DMEM. This study provides new and important clues regarding the major effects of Si-induced cell behavior as well as the precipitated apatite-inhibited hDPC behavior on these materials. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Impact Behavior of Three Notched All-Ceramic Restorations after Soaking in Artificial Saliva
Materials 2015, 8(7), 4479-4490; https://doi.org/10.3390/ma8074479
Received: 10 June 2015 / Revised: 29 June 2015 / Accepted: 16 July 2015 / Published: 20 July 2015
Cited by 3 | Viewed by 1720 | PDF Full-text (1100 KB) | HTML Full-text | XML Full-text
Abstract
Biomechanics play a critical role in influencing the clinical applications of all-ceramic dental restorations. The restorative biomaterials have to demonstrate mechanical durability in the oral environment because they are always exposed to a variety of oral environments. This study was designed to evaluate [...] Read more.
Biomechanics play a critical role in influencing the clinical applications of all-ceramic dental restorations. The restorative biomaterials have to demonstrate mechanical durability in the oral environment because they are always exposed to a variety of oral environments. This study was designed to evaluate the effect of soaking time, notch and saliva pH values on the impact energy of three commonly used all-ceramic materials for CAD/CAM. The leucite-reinforced glass ceramic (ProCAD), lithium disilicate glass ceramic (IPS e.max CAD) and zirconia-based ceramic materials (IPS e.max ZirCAD) were used. The experimental results indicated that the impact energy of ProCAD decreased with an increase in soaking time, but not for IPS e.max CAD and IPS e.max ZirCAD. The impact energy of the zirconia system was higher than leucite-reinforced and lithium disilicate-based ceramic systems. When subjected to preformed 0.5 mm U-shape notch on the bar specimen of 3 mm thick, the impact energy of the all-ceramic restorations revealed a markedly reduction of about 80%–90%, almost irrespective of dental compositions, which indicated the effect of flaw to a great degree. No statistically significant influence (p > 0.05) of pH values (4, 7 and 9) on impact energy was found for each group. It is concluded that the no matter which all-ceramic materials were used, it was appreciably sensitive to the presence of notches. The ceramic composition and microstructure have been shown to affect mechanical durability. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Experimental Study on Thermal Conductivity of Self-Compacting Concrete with Recycled Aggregate
Materials 2015, 8(7), 4457-4478; https://doi.org/10.3390/ma8074457
Received: 27 April 2015 / Revised: 6 July 2015 / Accepted: 7 July 2015 / Published: 20 July 2015
Cited by 7 | Viewed by 2154 | PDF Full-text (2287 KB) | HTML Full-text | XML Full-text
Abstract
The research focuses on the use of recycled aggregate (RA), from waste pieces generated during production in precast plants for self-compacting concrete (SCC) manufactured with a double sustainable goal: recycle manufacturing waste (consumption) and improvement of the thermal properties of the manufactured product [...] Read more.
The research focuses on the use of recycled aggregate (RA), from waste pieces generated during production in precast plants for self-compacting concrete (SCC) manufactured with a double sustainable goal: recycle manufacturing waste (consumption) and improvement of the thermal properties of the manufactured product (energy efficiency). For this purpose, a mechanical study to ensure technical feasibility of the concrete obtained has been conducted, as well as a thermal analysis of recycled SCC specimens of 50 N/mm2 resistance, with different RA doses (0%, 20%, 50% and 100%). The main parameters that characterize a SCC in both states, fresh (slump-flow) and hard (compressive strength), have been tested; also, a qualitative analysis of the thermal conductivity using infrared thermography (IRT) and quantitative analysis with heat flow meter at three temperatures 20 °C, 25 °C and 30 °C have been performed. The results suggest the existence of two different thermal behaviors: concretes with 0% and 20% of RA, and on the other hand concretes with 50% and 100% of RA. It has also demonstrated the validity of the IRT as sampling technique in estimating the thermal behavior of materials having reduced range of variation in parameters. Full article
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Open AccessReview Developments in PDT Sensitizers for Increased Selectivity and Singlet Oxygen Production
Materials 2015, 8(7), 4421-4456; https://doi.org/10.3390/ma8074421
Received: 28 January 2015 / Revised: 29 June 2015 / Accepted: 7 July 2015 / Published: 20 July 2015
Cited by 50 | Viewed by 3008 | PDF Full-text (1134 KB) | HTML Full-text | XML Full-text
Abstract
Photodynamic therapy (PDT) is a minimally-invasive procedure that has been clinically approved for treating certain types of cancers. This procedure takes advantage of the cytotoxic activity of singlet oxygen (1O2) and other reactive oxygen species (ROS) produced by visible [...] Read more.
Photodynamic therapy (PDT) is a minimally-invasive procedure that has been clinically approved for treating certain types of cancers. This procedure takes advantage of the cytotoxic activity of singlet oxygen (1O2) and other reactive oxygen species (ROS) produced by visible and NIR light irradiation of dye sensitizers following their accumulation in malignant cells. The main two concerns associated with certain clinically-used PDT sensitizers that have been influencing research in this arena are low selectivity toward malignant cells and low levels of 1O2 production in aqueous media. Solving the selectivity issue would compensate for photosensitizer concerns such as dark toxicity and aggregation in aqueous media. One main approach to enhancing dye selectivity involves taking advantage of key methods used in pharmaceutical drug delivery. This approach lies at the heart of the recent developments in PDT research and is a point of emphasis in the present review. Of particular interest has been the development of polymeric micelles as nanoparticles for delivering hydrophobic (lipophilic) and amphiphilic photosensitizers to the target cells. This review also covers methods employed to increase 1O2 production efficiency, including the design of two-photon absorbing sensitizers and triplet forming cyclometalated Ir(III) complexes. Full article
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Open AccessArticle Star-Shaped and Linear POSS-Polylactide Hybrid Copolymers
Materials 2015, 8(7), 4400-4420; https://doi.org/10.3390/ma8074400
Received: 9 June 2015 / Revised: 6 July 2015 / Accepted: 13 July 2015 / Published: 17 July 2015
Cited by 7 | Viewed by 1846 | PDF Full-text (1121 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Novel octakis-2[(6-hydroxyhexyl)thio]ethyl-octasilsesquioxane (POSS-S-OH) as well as heptaisobutyl-2[(6-hydroxyhexyl)thio]ethyl-octasilsesquioxane (iBu-POSS-S-OH) were synthesized. POSS structures, bearing both types of groups i.e., 2[(6-hydroxyhexyl)thio]ethyl and the vinyl ones, pendant from the octahedral cage are also described. The synthetic pathway involved thiol-ene click reaction of 6-mercapto-1-hexanol (MCH) to [...] Read more.
Novel octakis-2[(6-hydroxyhexyl)thio]ethyl-octasilsesquioxane (POSS-S-OH) as well as heptaisobutyl-2[(6-hydroxyhexyl)thio]ethyl-octasilsesquioxane (iBu-POSS-S-OH) were synthesized. POSS structures, bearing both types of groups i.e., 2[(6-hydroxyhexyl)thio]ethyl and the vinyl ones, pendant from the octahedral cage are also described. The synthetic pathway involved thiol-ene click reaction of 6-mercapto-1-hexanol (MCH) to octavinyloctasilsesquioxane (POSS-Vi), and heptaisobutylvinyloctasilsesquioxane (iBu-POSS-Vi), in the presence of 2,2′-azobisisobutyronitrile. The functionalized silsesquioxane cages of regular octahedral structure were used further as initiators for ring opening polymerization of L,L-dilactide, catalyzed by tin (II) 2-ethylhexanoate. The polymerization afforded biodegradable hybrid star shape and linear systems with an octasilsesquioxane cage as a core, bearing polylactide arm(s). Full article
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Open AccessArticle Experimental and Numerical Study on the Strength of Aluminum Extrusion Welding
Materials 2015, 8(7), 4389-4399; https://doi.org/10.3390/ma8074389
Received: 7 May 2015 / Revised: 22 June 2015 / Accepted: 13 July 2015 / Published: 17 July 2015
Cited by 5 | Viewed by 1955 | PDF Full-text (942 KB) | HTML Full-text | XML Full-text
Abstract
The quality of extrusion welding in the extruded hollow shapes is influenced significantly by the pressure and effective stress under which the material is being joined inside the welding chamber. However, extrusion welding was not accounted for in the past by the developers [...] Read more.
The quality of extrusion welding in the extruded hollow shapes is influenced significantly by the pressure and effective stress under which the material is being joined inside the welding chamber. However, extrusion welding was not accounted for in the past by the developers of finite element software packages. In this study, the strength of hollow extrusion profile with seam weld produced at different ram speeds was investigated experimentally and numerically. The experiments were performed on an extruded hollow aluminum profile which was suitable to obtain the tensile tests specimens from its seam weld’s region at both parallel to extrusion direction and perpendicular to extrusion direction. A new numerical modeling approach, which was recently proposed in literature, was used for numerical analyses of the study. The simulation results performed at different ram speeds were compared with the experimental results, and a good agreement was obtained. Full article
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Open AccessArticle Kaolinite Nanocomposite Platelets Synthesized by Intercalation and Imidization of Poly(styrene-co-maleic anhydride)
Materials 2015, 8(7), 4363-4388; https://doi.org/10.3390/ma8074363
Received: 7 June 2015 / Revised: 4 July 2015 / Accepted: 9 July 2015 / Published: 16 July 2015
Cited by 5 | Viewed by 2560 | PDF Full-text (4522 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A synthesis route is presented for the subsequent intercalation, exfoliation and surface modification of kaolinite (Kln) by an imidization reaction of high-molecular weight poly(styrene-co-maleic anhydride) or SMA in the presence of ammonium hydroxide. In a first step, the intercalation of ammonolyzed [...] Read more.
A synthesis route is presented for the subsequent intercalation, exfoliation and surface modification of kaolinite (Kln) by an imidization reaction of high-molecular weight poly(styrene-co-maleic anhydride) or SMA in the presence of ammonium hydroxide. In a first step, the intercalation of ammonolyzed SMA by guest displacement of intercalated dimethylsulfoxide has been proven. In a second step, the imidization of ammonolyzed SMA at 160 °C results in exfoliation of the kaolinite layers and deposition of poly(styrene-co-maleimide) or SMI nanoparticles onto the kaolinite surfaces. Compared with a physical mixture of Kln/SMI, the chemically reacted Kln/SMI provides more efficient exfoliation and hydrogen bonding between the nanoparticles and the kaolinite. The kaolinite nanocomposite particles are synthesized in aqueous dispersion with solid content of 65 wt %. The intercalation and exfoliation are optimized for a concentration ratio of Kln/SMI = 70:30, resulting in maximum intercalation and interlayer distance in combination with highest imide content. After thermal curing at 135 °C, the imidization proceeds towards a maximum conversion of the intermediate amic acid moieties. The changes in O–H stretching and kaolinite lattice vibrations have been illustrated by infrared and FT-Raman spectroscopy, which allow for a good quantification of concentration and imidization effects. Full article
(This article belongs to the Special Issue Developments in Organic Dyes and Pigments)
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Open AccessArticle Processing and Properties of Zirconia-Toughened Alumina Prepared by Gelcasting
Materials 2015, 8(7), 4344-4362; https://doi.org/10.3390/ma8074344
Received: 6 May 2015 / Revised: 10 July 2015 / Accepted: 10 July 2015 / Published: 16 July 2015
Cited by 4 | Viewed by 2187 | PDF Full-text (1997 KB) | HTML Full-text | XML Full-text
Abstract
Zirconia-toughened alumina (ZTA) using yttria-stabilised zirconia is a good option for ceramic-ceramic bearing couples for hip joint replacement. Gelcasting is a colloidal processing technique capable of producing complex products with a range of dimensions and materials by a relatively low-cost production process. Using [...] Read more.
Zirconia-toughened alumina (ZTA) using yttria-stabilised zirconia is a good option for ceramic-ceramic bearing couples for hip joint replacement. Gelcasting is a colloidal processing technique capable of producing complex products with a range of dimensions and materials by a relatively low-cost production process. Using gelcasting, ZTA samples were prepared, optimising the stages of fabrication, including slurry preparation with varying solid loadings, moulding and de-moulding, drying and sintering. Density, hardness, fracture toughness, flexural strength and grain size were observed relative to slurry solid loadings between 58 and 62 vol. %, as well as sintering temperatures of 1550 °C and 1650 °C. Optimal conditions found were plastic mould, 4000 g/mol PEG with 30 vol. % concentration, 61% solid loading and Ts = 1550 °C. ZTA samples of high density (maximum 99.1%), high hardness (maximum 1902 HV), high fracture toughness (maximum 5.43 MPa m1/2) and high flexural strength (maximum 618 MPa) were successfully prepared by gelcasting and pressureless sintering. Full article
(This article belongs to the Special Issue Bioceramics)
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Open AccessReview Nano Sensing and Energy Conversion Using Surface Plasmon Resonance (SPR)
Materials 2015, 8(7), 4332-4343; https://doi.org/10.3390/ma8074332
Received: 1 May 2015 / Revised: 20 June 2015 / Accepted: 26 June 2015 / Published: 16 July 2015
Cited by 4 | Viewed by 2404 | PDF Full-text (564 KB) | HTML Full-text | XML Full-text
Abstract
Nanophotonic technique has been attracting much attention in applications of nano-bio-chemical sensing and energy conversion of solar energy harvesting and enhanced energy transfer. One approach for nano-bio-chemical sensing is surface plasmon resonance (SPR) imaging, which can detect the material properties, such as density, [...] Read more.
Nanophotonic technique has been attracting much attention in applications of nano-bio-chemical sensing and energy conversion of solar energy harvesting and enhanced energy transfer. One approach for nano-bio-chemical sensing is surface plasmon resonance (SPR) imaging, which can detect the material properties, such as density, ion concentration, temperature, and effective refractive index in high sensitivity, label-free, and real-time under ambient conditions. Recent study shows that SPR can successfully detect the concentration variation of nanofluids during evaporation-induced self-assembly process. Spoof surface plasmon resonance based on multilayer metallo-dielectric hyperbolic metamaterials demonstrate SPR dispersion control, which can be combined with SPR imaging, to characterize high refractive index materials because of its exotic optical properties. Furthermore, nano-biophotonics could enable innovative energy conversion such as the increase of absorption and emission efficiency and the perfect absorption. Localized SPR using metal nanoparticles show highly enhanced absorption in solar energy harvesting. Three-dimensional hyperbolic metamaterial cavity nanostructure shows enhanced spontaneous emission. Recently ultrathin film perfect absorber is demonstrated with the film thickness is as low as ~1/50th of the operating wavelength using epsilon-near-zero (ENZ) phenomena at the wavelength close to SPR. It is expected to provide a breakthrough in sensing and energy conversion applications using the exotic optical properties based on the nanophotonic technique. Full article
(This article belongs to the Special Issue Plasmonic Materials)
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Open AccessArticle Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode
Materials 2015, 8(7), 4316-4331; https://doi.org/10.3390/ma8074316
Received: 7 May 2015 / Revised: 4 June 2015 / Accepted: 26 June 2015 / Published: 15 July 2015
Cited by 5 | Viewed by 1766 | PDF Full-text (856 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the deterioration of reinforced concrete with carbon fiber reinforced polymer (CFRP) anode after polarization. The steel in the concrete was first subjected to accelerated corrosion to various extents. Then, a polarization test was performed with the external attached CFRP as [...] Read more.
This paper investigates the deterioration of reinforced concrete with carbon fiber reinforced polymer (CFRP) anode after polarization. The steel in the concrete was first subjected to accelerated corrosion to various extents. Then, a polarization test was performed with the external attached CFRP as the anode and the steel reinforcement as the cathode. Carbon fiber reinforced mortar and conductive carbon paste as contact materials were used to adhere the CFRP anode to the concrete. Two current densities of 1244 and 2488 mA/m2, corresponding to the steel reinforcements were applied for 25 days. Electrochemical parameters were monitored during the test period. The deterioration mechanism that occurred at the CFRP/contact material interface was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The increase of feeding voltage and the failure of bonding was observed during polarization process, which might have resulted from the deterioration of the interface between the contact material and CFRP. The formation and accumulation of NaCl crystals at the contact material/CFRP interface were inferred to be the main causes of the failure at the interface. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells
Materials 2015, 8(7), 4299-4315; https://doi.org/10.3390/ma8074299
Received: 19 May 2015 / Revised: 25 June 2015 / Accepted: 8 July 2015 / Published: 14 July 2015
Cited by 20 | Viewed by 2595 | PDF Full-text (2808 KB) | HTML Full-text | XML Full-text
Abstract
Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu [...] Read more.
Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs’ responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding
Materials 2015, 8(7), 4287-4298; https://doi.org/10.3390/ma8074287
Received: 20 April 2015 / Revised: 2 July 2015 / Accepted: 3 July 2015 / Published: 14 July 2015
Cited by 3 | Viewed by 1950 | PDF Full-text (3422 KB) | HTML Full-text | XML Full-text
Abstract
Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would [...] Read more.
Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (Ø10 mm × 56 mm) made of alumina toughened zirconia (ATZ), as well as titanium grade 5, were bonded by glass solder on their end faces. As a control, a two-component adhesive glue was utilized. The samples were investigated without further treatment, after 30 and 90 days of storage in distilled water at room temperature, and after aging. All samples were subjected to quasi-static four-point-bending tests. We found that the glass solder bonding provided significantly higher bending strength than adhesive glue bonding. In contrast to the glued samples, the bending strength of the soldered samples remained unaltered by the storage and aging treatments. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses confirmed the presence of a stable solder-ceramic interface. Therefore, the glass solder technique represents a promising method for optimizing dental and orthopedic implant bondings. Full article
(This article belongs to the Special Issue Bioceramics)
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Open AccessArticle Preparation and Characterization of Surface Photocatalytic Activity with NiO/TiO2 Nanocomposite Structure
Materials 2015, 8(7), 4273-4286; https://doi.org/10.3390/ma8074273
Received: 24 May 2015 / Revised: 26 June 2015 / Accepted: 3 July 2015 / Published: 13 July 2015
Cited by 10 | Viewed by 2289 | PDF Full-text (1120 KB) | HTML Full-text | XML Full-text
Abstract
This study achieved a nanocomposite structure of nickel oxide (NiO)/titanium dioxide (TiO2) heterojunction on a TiO2 film surface. The photocatalytic activity of this structure evaluated by decomposing methylene blue (MB) solution was strongly correlated to the conductive behavior of the [...] Read more.
This study achieved a nanocomposite structure of nickel oxide (NiO)/titanium dioxide (TiO2) heterojunction on a TiO2 film surface. The photocatalytic activity of this structure evaluated by decomposing methylene blue (MB) solution was strongly correlated to the conductive behavior of the NiO film. A p-type NiO film of high concentration in contact with the native n-type TiO2 film, which resulted in a strong inner electrical field to effectively separate the photogenerated electron-hole pairs, exhibited a much better photocatalytic activity than the controlled TiO2 film. In addition, the photocatalytic activity of the NiO/TiO2 nanocomposite structure was enhanced as the thickness of the p-NiO film decreased, which was beneficial for the migration of the photogenerated carriers to the structural surface. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
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Open AccessArticle Photophysical Study of Polymer-Based Solar Cells with an Organo-Boron Molecule in the Active Layer
Materials 2015, 8(7), 4258-4272; https://doi.org/10.3390/ma8074258
Received: 20 May 2015 / Revised: 9 June 2015 / Accepted: 6 July 2015 / Published: 13 July 2015
Cited by 2 | Viewed by 1527 | PDF Full-text (1597 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Our group previously reported the synthesis of four polythiophene derivatives (P1–P4) used for solar cells. The cells were prepared under room conditions by spin coating, leading to low efficiencies. However, after the addition of 6-nitro-3-(E)-3-(4-dimethylaminophenyl)allylidene)-2,3-dihydrobenzo[d]-[1,3,2] oxazaborole (M1) to their active layers, the efficiencies [...] Read more.
Our group previously reported the synthesis of four polythiophene derivatives (P1–P4) used for solar cells. The cells were prepared under room conditions by spin coating, leading to low efficiencies. However, after the addition of 6-nitro-3-(E)-3-(4-dimethylaminophenyl)allylidene)-2,3-dihydrobenzo[d]-[1,3,2] oxazaborole (M1) to their active layers, the efficiencies of the cells showed approximately a two-fold improvement. In this paper, we study this enhancement mechanism by performing ultrafast transient absorption (TA) experiments on the active layer of the different cells. Our samples consisted of thin films of a mixture of PC61BM with the polythiophenes derivatives P1–P4. We prepared two versions of each sample, one including the molecule M1 and another without it. The TA data suggests that the efficiency improvement after addition of M1 is due not only to an extended absorption spectrum towards the infrared region causing a larger population of excitons but also to the possible creation of additional channels for transport of excitons and/or electrons to the PC61BM interface. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Wet-Induced Fabrication of Heterogeneous Hump-on-String Fibers
Materials 2015, 8(7), 4249-4257; https://doi.org/10.3390/ma8074249
Received: 25 April 2015 / Revised: 2 July 2015 / Accepted: 7 July 2015 / Published: 13 July 2015
Cited by 1 | Viewed by 1727 | PDF Full-text (1404 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Inspired by the high adhesiveness of the electrospun fiber, we propose a method to fabricate multi-scale heterogeneous hump-on-string fiber via the adsorption of nanoparticles, the NPCTi which is the hydrolysate of titanium tetrachloride (TiCl4) and the nanoparticles containing Al (NPCAl) which [...] Read more.
Inspired by the high adhesiveness of the electrospun fiber, we propose a method to fabricate multi-scale heterogeneous hump-on-string fiber via the adsorption of nanoparticles, the NPCTi which is the hydrolysate of titanium tetrachloride (TiCl4) and the nanoparticles containing Al (NPCAl) which is produced by the hydrolysis of Trimethylaluminium (TMA, Al(CH3)3). The water collection efficiency of the fibers can be easily controlled via changing not only the size of the beads but also the ratio of the Ti and Al. In addition, we introduce a computational fluid dynamics (CFD) simulation to show the pressure distribution of on the surface of the fibers, which gives another explanation regarding the high water collection efficiency. Full article
(This article belongs to the Special Issue Biobased Nanocomposite Functional Materials)
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Open AccessArticle Preparation and Properties of (YCa)(TiMn)O3−d Ceramics Interconnect of Solid Oxide Fuel Cells
Materials 2015, 8(7), 4239-4248; https://doi.org/10.3390/ma8074239
Received: 7 June 2015 / Revised: 26 June 2015 / Accepted: 6 July 2015 / Published: 10 July 2015
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Abstract
(YCa)(TiMn)O3–d ceramics prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. Y2Ti2O7 instead of YTiO3 formed when a mixture of Y2O [...] Read more.
(YCa)(TiMn)O3–d ceramics prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. Y2Ti2O7 instead of YTiO3 formed when a mixture of Y2O3 and TiO2 with Y/Ti ratio 1/1 were sintered in air. Y2Ti2O7, YTiO2.085 and some unknown phases were detected in Y0.6Ca0.4Ti0.6Mn0.4O3–d. Monophasic Y0.6Ca0.4Ti0.4Mn0.6O3–d ceramics were obtained after 1400–1500 °C sintering. Dense Y0.6Ca0.4Ti0.4Mn0.6O3–d with a density 4.69 g/cm3 was observed after 1500 °C/4 h sintering. Log σ for Y0.6Ca0.4Ti0.6Mn0.4O3–d increased from –3.73 Scm–1 at 350 °C to –2.14 Scm–1 at 700 °C. Log σ for Y0.6Ca0.4Ti0.4Mn0.6O3–d increased from –2.1 Scm–1 at 350 °C to –1.36 Scm–1 at 700 °C. Increasing Mn content decreased activation energy Ea and increased electrical conductivity. Reaction-sintering process is proved to be a simple and effective method to obtain (YCa)(TiMn)O3–d ceramics for interconnects in solid oxide fuel cells. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
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Open AccessArticle Dihydrogen Phosphate Stabilized Ruthenium(0) Nanoparticles: Efficient Nanocatalyst for The Hydrolysis of Ammonia-Borane at Room Temperature
Materials 2015, 8(7), 4226-4238; https://doi.org/10.3390/ma8074226
Received: 29 May 2015 / Revised: 1 July 2015 / Accepted: 7 July 2015 / Published: 10 July 2015
Cited by 6 | Viewed by 1750 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
Abstract
Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution [...] Read more.
Intensive efforts have been devoted to the development of new materials for safe and efficient hydrogen storage. Among them, ammonia-borane appears to be a promising candidate due to its high gravimetric hydrogen storage capacity. Ammonia-borane can release hydrogen on hydrolysis in aqueous solution under mild conditions in the presence of a suitable catalyst. Herein, we report the synthesis of ruthenium(0) nanoparticles stabilized by dihydrogenphosphate anions with an average particle size of 2.9 ± 0.9 nm acting as a water-dispersible nanocatalyst in the hydrolysis of ammonia-borane. They provide an initial turnover frequency (TOF) value of 80 min−1 in hydrogen generation from the hydrolysis of ammonia-borane at room temperature. Moreover, the high stability of these ruthenium(0) nanoparticles makes them long-lived and reusable nanocatalysts for the hydrolysis of ammonia-borane. They provide 56,800 total turnovers and retain ~80% of their initial activity even at the fifth catalytic run in the hydrolysis of ammonia-borane at room temperature. Full article
(This article belongs to the Special Issue Hydrogen Storage Materials)
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Open AccessArticle Experimental Studies on the Flammability and Fire Hazards of Photovoltaic Modules
Materials 2015, 8(7), 4210-4225; https://doi.org/10.3390/ma8074210
Received: 13 April 2015 / Revised: 17 June 2015 / Accepted: 1 July 2015 / Published: 9 July 2015
Cited by 8 | Viewed by 1702 | PDF Full-text (2124 KB) | HTML Full-text | XML Full-text
Abstract
Many of the photovoltaic (PV) systems on buildings are of sufficiently high voltages, with potential to cause or promote fires. However, research about photovoltaic fires is insufficient. This paper focuses on the flammability and fire hazards of photovoltaic modules. Bench-scale experiments based on [...] Read more.
Many of the photovoltaic (PV) systems on buildings are of sufficiently high voltages, with potential to cause or promote fires. However, research about photovoltaic fires is insufficient. This paper focuses on the flammability and fire hazards of photovoltaic modules. Bench-scale experiments based on polycrystalline silicon PV modules have been conducted using a cone calorimeter. Several parameters including ignition time (tig), mass loss, heat release rate (HRR), carbon monoxide (CO) and carbon dioxide (CO2) concentration, were investigated. The fire behaviours, fire hazards and toxicity of gases released by PV modules are assessed based on experimental results. The results show that PV modules under tests are inflammable with the critical heat flux of 26 kW/m2. This work will lead to better understanding on photovoltaic fires and how to help authorities determine the appropriate fire safety provisions for controlling photovoltaic fires. Full article
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Open AccessArticle Niobium-Doped Hydroxyapatite Bioceramics: Synthesis, Characterization and In Vitro Cytocompatibility
Materials 2015, 8(7), 4191-4209; https://doi.org/10.3390/ma8074191
Received: 14 April 2015 / Revised: 1 June 2015 / Accepted: 1 July 2015 / Published: 9 July 2015
Cited by 18 | Viewed by 2443 | PDF Full-text (6460 KB) | HTML Full-text | XML Full-text
Abstract
Doping calcium phosphates with ionic species can play an important role in biological responses promoting alkaline phosphatase activity, and, therefore inducing the generation of new bone. Thus, in this study, the synthesis of niobium-doped hydroxyapatite (Nb-HA) nanosize particles obtained by the precipitation process [...] Read more.
Doping calcium phosphates with ionic species can play an important role in biological responses promoting alkaline phosphatase activity, and, therefore inducing the generation of new bone. Thus, in this study, the synthesis of niobium-doped hydroxyapatite (Nb-HA) nanosize particles obtained by the precipitation process in aqueous media followed by thermal treatment is presented. The bioceramics were extensively characterized by X-ray diffraction, wavelength dispersive X-ray fluorescence spectrometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy analysis, transmission electron microscopy, atomic force microscopy and thermal analysis regarding their chemical composition, structure and morphology. The results showed that the precipitate dried at 110 °C was composed of amorphous calcium phosphate and HA, with polidisperse particles ranging from micro to nano dimensions. After the thermal treatment at 900 °C, the bioceramic system evolved predominantly to HA crystalline phase, with evident features of particle sintering and reduction of surface area. Moreover, the addition of 10 mol% of niobium salt precursor during the synthesis indicated the complete incorporation of the Nb(V) species in the HA crystals with detectable changes in the original lattice parameters. Furthermore, the incorporation of Nb ions caused a significant refinement on the average particle size of HA. Finally, the preliminary cytocompatibility response of the biomaterials was accessed by human osteoblast cell culture using MTT and resazurin assays, which demonstrated no cytotoxicity of the Nb-alloyed hydroxyapatite. Thus, these findings seem promising for developing innovative Nb-doped calcium phosphates as artificial biomaterials for potential use in bone replacements and repair. Full article
(This article belongs to the Special Issue Bioceramics)
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Open AccessArticle Microscopic Characterization of Individual Submicron Bubbles during the Layer-by-Layer Deposition: Towards Creating Smart Agents
Materials 2015, 8(7), 4176-4190; https://doi.org/10.3390/ma8074176
Received: 11 December 2014 / Revised: 13 June 2015 / Accepted: 29 June 2015 / Published: 8 July 2015
Cited by 2 | Viewed by 1550 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We investigated the individual properties of various polyion-coated bubbles with a mean diameter ranging from 300 to 500 nm. Dark field microscopy allows one to track the individual particles of the submicron bubbles (SBs) encapsulated by the layer-by-layer (LbL) deposition of cationic and [...] Read more.
We investigated the individual properties of various polyion-coated bubbles with a mean diameter ranging from 300 to 500 nm. Dark field microscopy allows one to track the individual particles of the submicron bubbles (SBs) encapsulated by the layer-by-layer (LbL) deposition of cationic and anionic polyelectrolytes (PEs). Our focus is on the two-step charge reversals of PE-SB complexes: the first is a reversal from negatively charged bare SBs with no PEs added to positive SBs encapsulated by polycations (monolayer deposition), and the second is overcharging into negatively charged PE-SB complexes due to the subsequent addition of polyanions (double-layer deposition). The details of these phenomena have been clarified through the analysis of a number of trajectories of various PE-SB complexes that experience either Brownian motion or electrophoresis. The contrasted results obtained from the analysis were as follows: an amount in excess of the stoichiometric ratio of the cationic polymers was required for the first charge-reversal, whereas the stoichiometric addition of the polyanions lead to the electrical neutralization of the PE-SB complex particles. The recovery of the stoichiometry in the double-layer deposition paves the way for fabricating multi-layered SBs encapsulated solely with anionic and cationic PEs, which provides a simple protocol to create smart agents for either drug delivery or ultrasound contrast imaging. Full article
(This article belongs to the Special Issue Smart Materials)
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