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Materials, Volume 11, Issue 2 (February 2018)

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Cover Story (view full-size image) Metal–elastomer interfacial systems—often encountered in stretchable electronics—demonstrate [...] Read more.
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Open AccessArticle Facile Fabrication of 100% Bio-based and Degradable Ternary Cellulose/PHBV/PLA Composites
Materials 2018, 11(2), 330; https://doi.org/10.3390/ma11020330
Received: 13 January 2018 / Revised: 8 February 2018 / Accepted: 20 February 2018 / Published: 24 February 2018
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Abstract
Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials.
[...] Read more.
Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials. The effects of ball milling on the physicochemical properties of pulp cellulose fibers, and the ball-milled cellulose particles on the morphology and mechanical properties of PHBV/PLA blends, were investigated experimentally and statistically. The results showed that more ball-milling time resulted in a smaller particle size and lower crystallinity by way of mechanical disintegration. Filling PHBV/PLA blends with the ball-milled celluloses dramatically increased the stiffness at all of the levels of particle size and filling content, and improved their elongation at the break and fracture work at certain levels of particle size and filling content. It was also found that the high filling content of the ball-milled cellulose particles was detrimental to the mechanical properties for the resultant composite materials. The ternary cellulose/PHBV/PLA composite materials have some potential applications, such as in packaging materials and automobile inner decoration parts. Furthermore, filling content contributes more to the variations of their mechanical properties than particle size does. Statistical analysis combined with experimental tests provide a new pathway to quantitatively evaluate the effects of multiple variables on a specific property, and figure out the dominant one for the resultant composite materials. Full article
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Open AccessFeature PaperArticle Improved Formability of Mg-AZ80 Alloy under a High Strain Rate in Expanding-Ring Experiments
Materials 2018, 11(2), 329; https://doi.org/10.3390/ma11020329
Received: 15 January 2018 / Revised: 10 February 2018 / Accepted: 14 February 2018 / Published: 24 February 2018
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Abstract
Magnesium alloys offer a favored alternative to steels and aluminum alloys due to their low density and relatively high specific strength. Their application potentials are, however, impeded by poor formability at room temperature. In the current work, improved formability for the commercial magnesium
[...] Read more.
Magnesium alloys offer a favored alternative to steels and aluminum alloys due to their low density and relatively high specific strength. Their application potentials are, however, impeded by poor formability at room temperature. In the current work, improved formability for the commercial magnesium AZ80 alloy was attained through the application of the high-rate electro-magnetic forming (EMF) technique. With the EMF system, elongation of 0.2 was achieved while only 0.11 is obtained through quasistatic loading. Systematic microstructural and textural investigations prior, during and post deformation under high strain-rate experiments were carried out using electron back-scattered diffraction (EBSD) and other microscopic techniques. The analysis indicates that enhanced elongation is achieved as a result of the combination of deformation, comprising basal and non-basal slip systems, twinning and dynamic recrystallization. An adopted EMF-forming technique is tested which results in enhanced elongation without failure and a higher degree of dynamically annealed microstructure. Full article
(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)
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Open AccessArticle Effects of Temperature and Pressure of Hot Isostatic Pressing on the Grain Structure of Powder Metallurgy Superalloy
Materials 2018, 11(2), 328; https://doi.org/10.3390/ma11020328
Received: 18 January 2018 / Revised: 7 February 2018 / Accepted: 14 February 2018 / Published: 24 February 2018
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Abstract
The microstructure with homogeneously distributed grains and less prior particle boundary (PPB) precipitates is always desired for powder metallurgy superalloys after hot isostatic pressing (HIPping). In this work, we studied the effects of HIPping parameters, temperature and pressure on the grain structure in
[...] Read more.
The microstructure with homogeneously distributed grains and less prior particle boundary (PPB) precipitates is always desired for powder metallurgy superalloys after hot isostatic pressing (HIPping). In this work, we studied the effects of HIPping parameters, temperature and pressure on the grain structure in PM superalloy FGH96, by means of scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM) and Time-of-flight secondary ion spectrometry (ToF-SIMS). It was found that temperature and pressure played different roles in controlling PPB precipitation and grain structure during HIPping, the tendency of grain coarsening under high temperature could be inhibited by increasing HIPping pressure which facilitates the recrystallization. In general, relatively high temperature and pressure of HIPping were preferred to obtain an as-HIPped superalloy FGH96 with diminished PPB precipitation and homogeneously refined grains. Full article
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Open AccessArticle Mesoscopic Constitutive Model for Predicting Failure of Bulk Metallic Glass Composites Based on the Free-Volume Model
Materials 2018, 11(2), 327; https://doi.org/10.3390/ma11020327
Received: 7 December 2017 / Revised: 23 January 2018 / Accepted: 21 February 2018 / Published: 24 February 2018
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Abstract
A meso-mechanical damage model is developed to predict the tensile damage behaviors of bulk metallic glass composites (BMGCs) toughened by ductile particles. In this model, the deformation behaviors of the BMG matrix and particles are described by the free volume model and Ludwik
[...] Read more.
A meso-mechanical damage model is developed to predict the tensile damage behaviors of bulk metallic glass composites (BMGCs) toughened by ductile particles. In this model, the deformation behaviors of the BMG matrix and particles are described by the free volume model and Ludwik flow equation, respectively. Weng’s dual-phase method is used to establish the relationship between the constituents and the composite system. The strain-based Weibull probability distribution function and percolation theory are adopted in characterizing the evolution of shear bands leading to the progressive failure of BMGCs. Moreover, the present model is performed under strain-controlled loading. Comparing to experiments on various BMGCs, the predictions are in good agreement with the measured results, which confirms that the present model successfully depicts the composite properties, such as yield strength, uniform deformation and strain softening elongation. Full article
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Open AccessReview Recent Evidence on Bioactive Glass Antimicrobial and Antibiofilm Activity: A Mini-Review
Materials 2018, 11(2), 326; https://doi.org/10.3390/ma11020326
Received: 25 January 2018 / Revised: 14 February 2018 / Accepted: 17 February 2018 / Published: 24 February 2018
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Abstract
Bone defects caused by trauma or pathological events are major clinical and socioeconomic burdens. Thus, the efforts of regenerative medicine have been focused on the development of non-biodegradable materials resembling bone features. Consequently, the use of bioactive glass as a promising alternative to
[...] Read more.
Bone defects caused by trauma or pathological events are major clinical and socioeconomic burdens. Thus, the efforts of regenerative medicine have been focused on the development of non-biodegradable materials resembling bone features. Consequently, the use of bioactive glass as a promising alternative to inert graft materials has been proposed. Bioactive glass is a synthetic silica-based material with excellent mechanical properties able to bond to the host bone tissue. Indeed, when immersed in physiological fluids, bioactive glass reacts, developing an apatite layer on the granule’s surface, playing a key role in the osteogenesis process. Moreover, the contact of bioactive glass with biological fluids results in the increase of osmotic pressure and pH due to the leaching of ions from granules’ surface, thus making the surrounding environment hostile to microbial growth. The bioactive glass antimicrobial activity is effective against a wide selection of aerobic and anaerobic bacteria, either in planktonic or sessile forms. Furthermore, bioglass is able to reduce pathogens’ biofilm production. For the aforementioned reasons, the use of bioactive glass might be a promising solution for the reconstruction of bone defects, as well as for the treatment and eradication of bone infections, characterized by bone necrosis and destruction of the bone structure. Full article
(This article belongs to the Special Issue Bioactive Glasses 2017)
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Open AccessFeature PaperArticle TopUp SERS Substrates with Integrated Internal Standard
Materials 2018, 11(2), 325; https://doi.org/10.3390/ma11020325
Received: 11 December 2017 / Revised: 12 February 2018 / Accepted: 20 February 2018 / Published: 24 February 2018
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Abstract
Surface-enhanced Raman spectroscopy (SERS) is known as a molecular-specific and highly sensitive method. In order to enable the routine application of SERS, powerful SERS substrates are of great importance. Within this manuscript, a TopUp SERS substrate is introduced which is fabricated by a
[...] Read more.
Surface-enhanced Raman spectroscopy (SERS) is known as a molecular-specific and highly sensitive method. In order to enable the routine application of SERS, powerful SERS substrates are of great importance. Within this manuscript, a TopUp SERS substrate is introduced which is fabricated by a top-down process based on microstructuring as well as a bottom-up generation of silver nanostructures. The Raman signal of the support material acts as an internal standard in order to improve the quantification capabilities. The analyte molecule coverage of sulfamethoxazole on the surface of the nanostructures is characterized by the SERS signal evolution fitted by a Langmuir–Freundlich isotherm. Full article
(This article belongs to the Special Issue SERS-Active Substrates)
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Open AccessReview Fe3O4 Nanoparticles in Targeted Drug/Gene Delivery Systems
Materials 2018, 11(2), 324; https://doi.org/10.3390/ma11020324
Received: 31 January 2018 / Revised: 21 February 2018 / Accepted: 21 February 2018 / Published: 23 February 2018
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Abstract
Fe3O4 nanoparticles (NPs), the most traditional magnetic nanoparticles, have received a great deal of attention in the biomedical field, especially for targeted drug/gene delivery systems, due to their outstanding magnetism, biocompatibility, lower toxicity, biodegradability, and other features. Naked Fe3
[...] Read more.
Fe3O4 nanoparticles (NPs), the most traditional magnetic nanoparticles, have received a great deal of attention in the biomedical field, especially for targeted drug/gene delivery systems, due to their outstanding magnetism, biocompatibility, lower toxicity, biodegradability, and other features. Naked Fe3O4 NPs are easy to aggregate and oxidize, and thus are often made with various coatings to realize superior properties for targeted drug/gene delivery. In this review, we first list the three commonly utilized synthesis methods of Fe3O4 NPs, and their advantages and disadvantages. In the second part, we describe coating materials that exhibit noticeable features that allow functionalization of Fe3O4 NPs and summarize their methods of drug targeting/gene delivery. Then our efforts will be devoted to the research status and progress of several different functionalized Fe3O4 NP delivery systems loaded with chemotherapeutic agents, and we present targeted gene transitive carriers in detail. In the following section, we illuminate the most effective treatment systems of the combined drug and gene therapy. Finally, we propose opportunities and challenges of the clinical transformation of Fe3O4 NPs targeting drug/gene delivery systems. Full article
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Open AccessArticle The Preparation, Characterization, Mechanical and Antibacterial Properties of GO-ZnO Nanocomposites with a Poly(l-lactide)-Modified Surface
Materials 2018, 11(2), 323; https://doi.org/10.3390/ma11020323
Received: 27 December 2017 / Revised: 12 February 2018 / Accepted: 13 February 2018 / Published: 23 February 2018
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Abstract
Graphene oxide (GO) was employed for the preparation of GO-zinc oxide (ZnO). The hydroxyl group on the surface was exploited to trigger the l-lactide ring-opening polymerization. A composite material with poly(l-lactide) (PLLA) chains grafted to the GO-ZnO surface, GO-ZnO-PLLA, was
[...] Read more.
Graphene oxide (GO) was employed for the preparation of GO-zinc oxide (ZnO). The hydroxyl group on the surface was exploited to trigger the l-lactide ring-opening polymerization. A composite material with poly(l-lactide) (PLLA) chains grafted to the GO-ZnO surface, GO-ZnO-PLLA, was prepared. The results demonstrated that the employed method allowed one-step, rapid grafting of PLLA to the GO-ZnO surface. The chemical structure of the GO surface was altered by improved dispersion of GO-ZnO in organic solvents, thus enhancing the GO-ZnO dispersion in the PLLA matrix and the interface bonding with PLLA. Subsequently, composite films, GO-ZnO-PLLA and GO-ZnO-PLLA/PLLA, were prepared. The changes in interface properties and mechanical properties were studied. Furthermore, the antibacterial performance of nano-ZnO was investigated. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle 3D Graphene-Nitrogen Doped Carbon Nanotubes Network Modified Electrode as Sensing Materials for the Determination of Urapidil
Materials 2018, 11(2), 322; https://doi.org/10.3390/ma11020322
Received: 30 January 2018 / Revised: 11 February 2018 / Accepted: 12 February 2018 / Published: 23 February 2018
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Abstract
In this work, a three dimensional (3D) graphene-nitrogen doped carbon nanotubes (G-NCNTs) network was successfully fabricated on the surface of a glassy carbon (GC) electrode using the pulse potential method (PPM) in a graphene oxide-nitrogen doped carbon nanotubes (GO-NCNTs) dispersion. The morphological and
[...] Read more.
In this work, a three dimensional (3D) graphene-nitrogen doped carbon nanotubes (G-NCNTs) network was successfully fabricated on the surface of a glassy carbon (GC) electrode using the pulse potential method (PPM) in a graphene oxide-nitrogen doped carbon nanotubes (GO-NCNTs) dispersion. The morphological and characteristics of GO-NCNTs and G-NCNTs nanocomposites were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy, Raman spectroscopy, and electrochemical experiments. The 3DG-NCNTs network was applied as a new voltammetric material for the fabrication of an electrochemical platform for determination of urapidil. Systematic electrochemical tests demonstrate that the 3DG-NCNTs network modified GC electrode can effectively increase the response to the oxidation of urapidil. Under the optimum conditions, the electrochemical response was linear with urapidil concentrations in the range of 1.0 × 10−8~2.0 × 10−6 mol·L−1, while a low detection limit of 5.0 × 10−9 mol·L−1 was obtained for urapidil. Moreover, the proposed sensing platform exhibited good results for sensitivity, reproducibility, selectivity, and stability, which makes it very suitable for use as an ideal inexpensive and rapid analytical method applicable for complex drug matrices. Full article
(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)
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Open AccessFeature PaperReview Emerging Nanomedicine Therapies to Counter the Rise of Methicillin-Resistant Staphylococcus aureus
Materials 2018, 11(2), 321; https://doi.org/10.3390/ma11020321
Received: 19 January 2018 / Revised: 14 February 2018 / Accepted: 19 February 2018 / Published: 23 February 2018
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Abstract
In a recent report, the World Health Organisation (WHO) classified antibiotic resistance as one of the greatest threats to global health, food security, and development. Methicillin-resistant Staphylococcus aureus (MRSA) remains at the core of this threat, with persistent and resilient strains detectable in
[...] Read more.
In a recent report, the World Health Organisation (WHO) classified antibiotic resistance as one of the greatest threats to global health, food security, and development. Methicillin-resistant Staphylococcus aureus (MRSA) remains at the core of this threat, with persistent and resilient strains detectable in up to 90% of S. aureus infections. Unfortunately, there is a lack of novel antibiotics reaching the clinic to address the significant morbidity and mortality that MRSA is responsible for. Recently, nanomedicine strategies have emerged as a promising therapy to combat the rise of MRSA. However, these approaches have been wide-ranging in design, with few attempts to compare studies across scientific and clinical disciplines. This review seeks to reconcile this discrepancy in the literature, with specific focus on the mechanisms of MRSA infection and how they can be exploited by bioactive molecules that are delivered by nanomedicines, in addition to utilisation of the nanomaterials themselves as antibacterial agents. Finally, we discuss targeting MRSA biofilms using nano-patterning technologies and comment on future opportunities and challenges for MRSA treatment using nanomedicine. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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Open AccessArticle Microstructural Evolution of AlCoCrFeNiSi High-Entropy Alloy Powder during Mechanical Alloying and Its Coating Performance
Materials 2018, 11(2), 320; https://doi.org/10.3390/ma11020320
Received: 25 October 2017 / Revised: 20 February 2018 / Accepted: 20 February 2018 / Published: 23 February 2018
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Abstract
High-entropy alloys (HEAs) are promising structural materials due to their excellent comprehensive performances. The use of mechanically alloyed powders to deposit HEA coatings through atmospheric plasma spraying (APS) is an effective approach that can broaden the application areas of the HEAs. In this
[...] Read more.
High-entropy alloys (HEAs) are promising structural materials due to their excellent comprehensive performances. The use of mechanically alloyed powders to deposit HEA coatings through atmospheric plasma spraying (APS) is an effective approach that can broaden the application areas of the HEAs. In this paper, a ductility–brittleness AlCoCrFeNiSi system was chosen as an object of study, and the detailed evolution of the surface morphology, particle size distribution, and microstructure of the powder during mechanical alloying was investigated. An AlCoCrFeNiSi HEA coating was deposited using powder milled for 10 h, which can be used as an ideal feedstock for APS. The surface morphology, microstructure, microhardness, and wear behavior of the coating at room temperature were investigated. The results showed that as the milling time increased, the particle size first increased, and then decreased. At the milling time of 10 h, simple body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases were formed. After spraying, the lamellar structure inside a single particle disappeared. An ordered BCC phase was detected, and the diffraction peaks of the Si element also disappeared, which indicates that phase transformation occurred during plasma spraying. A transmission electron microscopy analysis showed that nanometer crystalline grains with a grain size of about 30 nm existed in the APS coating. For the coating, an average microhardness of 612 ± 41 HV was obtained. Adhesive wear, tribo-oxidation wear, and slight abrasion wear took place during the wear test. The coating showed good wear resistance, with a volume wear rate of 0.38 ± 0.08 × 10−4 mm3·N−1·m−1, which makes it a promising coating for use in abrasive environments. Full article
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Open AccessLetter Bottom–Up Electrodeposition of Large-Scale Nanotwinned Copper within 3D Through Silicon Via
Materials 2018, 11(2), 319; https://doi.org/10.3390/ma11020319
Received: 27 December 2017 / Revised: 17 February 2018 / Accepted: 19 February 2018 / Published: 23 February 2018
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Abstract
This paper is the first to report a large-scale directcurrent electrodeposition of columnar nanotwinned copper within through silicon via (TSV) with a high aspect ratio (~4). With this newly developed technique, void-free nanotwinned copper array could be fabricated in low current density (30
[...] Read more.
This paper is the first to report a large-scale directcurrent electrodeposition of columnar nanotwinned copper within through silicon via (TSV) with a high aspect ratio (~4). With this newly developed technique, void-free nanotwinned copper array could be fabricated in low current density (30 mA/cm2) and convection conditions (300 rpm), which are the preconditions for copper deposition with a uniform deep-hole microstructure. The microstructure of a whole cross-section of deposited copper array was made up of (111) orientated columnar grains with parallel nanoscale twins that had thicknesses of about 22 nm. The hardness was also uniform along the growth direction, with 2.34 and 2.68 GPa for the top and bottom of the TSV, respectively. The gelatin additive is also first reported hereas a key factor in forming nanoscale twins by adsorbing on the cathode surface, in order to enhance the overpotential for cathodic reaction during the copper deposition process. Full article
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Open AccessArticle Effect of Silver-Emitting Filler on Antimicrobial and Mechanical Properties of Soft Denture Lining Material
Materials 2018, 11(2), 318; https://doi.org/10.3390/ma11020318
Received: 29 January 2018 / Revised: 14 February 2018 / Accepted: 18 February 2018 / Published: 22 February 2018
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Abstract
Colonization of silicone-based soft lining materials by pathogenic yeast-type fungi is a common problem associated with the use of dentures. In this study, silver sodium hydrogen zirconium phosphate (SSHZP) was introduced into polydimethylsiloxane-based material as an antimicrobial filler at concentrations of 0.25, 0.5,
[...] Read more.
Colonization of silicone-based soft lining materials by pathogenic yeast-type fungi is a common problem associated with the use of dentures. In this study, silver sodium hydrogen zirconium phosphate (SSHZP) was introduced into polydimethylsiloxane-based material as an antimicrobial filler at concentrations of 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 14% (w/w). The in vitro antimicrobial efficacy was investigated. Candida albicans was used as a characteristic representative of pathogenic oral microflora. Staphylococcus aureus and Escherichia coli were used as the typical Gram-positive and Gram-negative bacterial strains, respectively. The effect of filler addition on the Shore A hardness, tensile strength, tensile bond strength, sorption, and solubility was investigated. An increase in the filler concentration resulted in an increase in hardness, sorption, and solubility, and for the highest concentration, a decrease in bond strength. The favorable combination of antimicrobial efficacy with other properties was achieved at filler concentrations ranging from 2% to 10%. These composites exhibited mechanical properties similar to the material without the antimicrobial filler and enhanced in vitro antimicrobial efficiency. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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Open AccessArticle Ultrarapid Multimode Microwave Synthesis of Nano/Submicron β-SiC
Materials 2018, 11(2), 317; https://doi.org/10.3390/ma11020317
Received: 1 December 2017 / Revised: 2 February 2018 / Accepted: 2 February 2018 / Published: 22 February 2018
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This paper presents the design, development and realization of a fast and novel process for the synthesis of 3C silicon carbide (β-SiC) nanorods and submicron powder. Using SiO2 (or Si) and activated carbon (AC), this process allows β-SiC to be synthesized with
[...] Read more.
This paper presents the design, development and realization of a fast and novel process for the synthesis of 3C silicon carbide (β-SiC) nanorods and submicron powder. Using SiO2 (or Si) and activated carbon (AC), this process allows β-SiC to be synthesized with almost 100% purity in timeframes of seconds or minutes using multimode microwave rotary tube reactors under open-air conditions. The synthesis temperature used was 1460 ± 50 °C for Si + AC and 1660 ± 50 °C for SiO2 + AC. The shortest β-SiC synthesis time achieved was about 20 s for Si + AC and 100 s for SiO2 + AC. This novel synthesis method allows for scaled-up flow processes in the rapid industrial-scale production of β-SiC, having advantages of time/energy saving and carbon dioxide emission reduction over comparable modern processes. Full article
(This article belongs to the Section Carbon Materials)
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Open AccessArticle Carbon-Fibre-Reinforced SiC Composite (C/SiSiC) as an Alternative Material for Endoprosthesis: Fabrication, Mechanical and In-Vitro Biological Properties
Materials 2018, 11(2), 316; https://doi.org/10.3390/ma11020316
Received: 19 January 2018 / Revised: 12 February 2018 / Accepted: 13 February 2018 / Published: 22 February 2018
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Abstract
Particle-induced periprosthetic osteolysis and subsequent aseptic implant loosening are a major cause of compromising the long-term results of total joint replacements. To date, no implant has been able to mirror radically the tribological factors (friction/lubrication/wear) of in vivo tribological pairings. Carbon-Fibre Reinforced SiC-Composites
[...] Read more.
Particle-induced periprosthetic osteolysis and subsequent aseptic implant loosening are a major cause of compromising the long-term results of total joint replacements. To date, no implant has been able to mirror radically the tribological factors (friction/lubrication/wear) of in vivo tribological pairings. Carbon-Fibre Reinforced SiC-Composites (C/SiSiC), a material primarily developed for brake technology, has the opportunity to fulfil this requirement. Until now, the material itself has not been used in medicine. The aim of this investigation was to test the suitability of C/SiSiC ceramics as a new material for bearing couples in endoprosthetics. After the preparation of the composites flexural strength was determined as well as the Young’s-modulus and the coefficient of friction. To investigate in vitro biological properties, MG 63 and primary human osteoblasts were cultured on C/SiSiC composites. To review the proliferation, the cytotoxicity standardized tests were used. The cell morphology was observed by light microscopy, ESEM, confocal and 3D-laserscanning microscopy. C/SiSiC possesses a high resistance to wear. Cells exhibited no significant alterations in morphology. Vitality was not impaired by contact with the ceramic composite. There was no higher cytotoxicity to observe. Regarding these results, C/SiSiC ceramics seem to be biologically and mechanically appropriate for orthopaedic applications. Full article
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Open AccessArticle Electrical/Mechanical Monitoring of Shape Memory Alloy Reinforcing Fibers Obtained by Pullout Tests in SMA/Cement Composite Materials
Materials 2018, 11(2), 315; https://doi.org/10.3390/ma11020315
Received: 20 September 2017 / Revised: 15 February 2018 / Accepted: 18 February 2018 / Published: 22 February 2018
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Abstract
Self-healing is an essential property of smart concrete structures. In contrast to other structural metals, shape memory alloys (SMAs) offer two unique effects: shape memory effects, and superelastic effects. Composites composed of SMA wires and conventional cements can overcome the mechanical weaknesses associated
[...] Read more.
Self-healing is an essential property of smart concrete structures. In contrast to other structural metals, shape memory alloys (SMAs) offer two unique effects: shape memory effects, and superelastic effects. Composites composed of SMA wires and conventional cements can overcome the mechanical weaknesses associated with tensile fractures in conventional concretes. Under specialized environments, the material interface between the cementitious component and the SMA materials plays an important role in achieving the enhanced mechanical performance and robustness of the SMA/cement interface. This material interface is traditionally evaluated in terms of mechanical aspects, i.e., strain–stress characteristics. However, the current work attempts to simultaneously characterize the mechanical load-displacement relationships synchronized with impedance spectroscopy as a function of displacement. Frequency-dependent impedance spectroscopy is tested as an in situ monitoring tool for structural variations in smart composites composed of non-conducting cementitious materials and conducting metals. The artificial geometry change in the SMA wires is associated with an improved anchoring action that is compatible with the smallest variation in resistance compared with prismatic SMA wires embedded into a cement matrix. The significant increase in resistance is interpreted to be associated with the slip of the SMA fibers following the elastic deformation and the debonding of the SMA fiber/matrix. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Gentamicin-Releasing Mesoporous ZnO Structures
Materials 2018, 11(2), 314; https://doi.org/10.3390/ma11020314
Received: 29 January 2018 / Revised: 11 February 2018 / Accepted: 17 February 2018 / Published: 22 February 2018
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Abstract
Among metal oxides, zinc oxide (ZnO) is one of the most attractive materials thanks to its biocompatible and biodegradable properties along with the existence of various morphologies featuring piezoelectric, semiconducting and photocatalytic activities. All of these structures were successfully prepared and tested for
[...] Read more.
Among metal oxides, zinc oxide (ZnO) is one of the most attractive materials thanks to its biocompatible and biodegradable properties along with the existence of various morphologies featuring piezoelectric, semiconducting and photocatalytic activities. All of these structures were successfully prepared and tested for numerous applications, including optoelectronics, sensors and biomedical ones. In the last case, biocompatible ZnO nanomaterials positively influenced cells growth and tissue regeneration as well, promoting wound healing and new bone formation. Despite showing high surface areas, ZnO morphologies generally lack an intrinsic mesoporous structure, strongly limiting the investigation of the corresponding drug loading and release properties. Within this scope, this study focuses on the adsorption and release properties of high surface area, mesoporous ZnO structures using gentamicin sulfate (GS), a well known antibiotic against bacterial infections especially in orthopedics. The particular ZnO morphology was achieved starting from sputtered porous zinc layers, finally converted into ZnO by thermal oxidation. By taking advantage of this mesoporous framework, GS was successfully adsorbed within the ZnO matrix and the kinetic release profile evaluated for up to seven days. The adsorption of GS was successfully demonstrated, with a maximum amount of 263 mg effectively loaded per gram of active material. Then, fast kinetic release was obtained in vitro by simple diffusion mechanism, thus opening further possibilities of smart pore and surface engineering to improve the controlled delivery. Full article
(This article belongs to the Special Issue Selected papers from EUROMAT 2017 Conference—Biomaterials)
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Open AccessArticle DFT Insights into the Role of Relative Positions of Fe and N Dopants on the Structure and Properties of TiO2
Materials 2018, 11(2), 313; https://doi.org/10.3390/ma11020313
Received: 6 February 2018 / Revised: 11 February 2018 / Accepted: 12 February 2018 / Published: 22 February 2018
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Abstract
The location and nature of the doped elements strongly affect the structural, electronic and optical properties of TiO2. To tailor the band structure and modify the photoelectrochemical properties of TiO2, a pair of dopants is selected. Fe and N
[...] Read more.
The location and nature of the doped elements strongly affect the structural, electronic and optical properties of TiO2. To tailor the band structure and modify the photoelectrochemical properties of TiO2, a pair of dopants is selected. Fe and N atoms are inserted in the TiO2 network at substitutional and interstitial sites with different relative distances. The main objective behind the different locations and sites of the doped elements is to banish the isolated unoccupied states from the forbidden region that normally annihilates the photogenerated carriers. Fe at the Ti site and N at the O site doped in the TiO2 network separated at a distance of 7.805 Å provided a suitable configuration of dopant atoms in terms of geometry and band structure. Moreover, the optical properties showed a notable shift to the visible regime. Individual dopants either introduced isolated unoccupied states in the band gap or disturbed the fermi level and structural properties. Furthermore, the other co-doped configurations showed no remarkable band shift, as well as exhibiting a suitable band structure. Resultantly, comparing the band structure and optical properties, it is argued that Fe (at Ti) and N (at O) doped at a distance of 7.805 Å would strongly improve the photoelectrochemical properties of TiO2. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Further Theoretical Insight into the Mechanical Properties of Polycaprolactone Loaded with Organic–Inorganic Hybrid Fillers
Materials 2018, 11(2), 312; https://doi.org/10.3390/ma11020312
Received: 29 December 2017 / Revised: 14 February 2018 / Accepted: 17 February 2018 / Published: 21 February 2018
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Abstract
Experimental/theoretical analyses have already been performed on poly(ε-caprolactone) (PCL) loaded with organic–inorganic fillers (PCL/TiO2 and PCL/ZrO2) to find a correlation between the results from the small punch test and Young’s modulus of the materials. PCL loaded with Ti2 (PCL =
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Experimental/theoretical analyses have already been performed on poly(ε-caprolactone) (PCL) loaded with organic–inorganic fillers (PCL/TiO2 and PCL/ZrO2) to find a correlation between the results from the small punch test and Young’s modulus of the materials. PCL loaded with Ti2 (PCL = 12, TiO2 = 88 wt %) and Zr2 (PCL = 12, ZrO2 = 88 wt %) hybrid fillers showed better performances than those obtained for the other particle composition. In this context, the aim of current research is to provide further insight into the mechanical properties of PCL loaded with sol–gel-synthesized organic–inorganic hybrid fillers for bone tissue engineering. For this reason, theoretical analyses were performed by the finite element method. The results from the small punch test and Young’s modulus of the materials were newly correlated. The obtained values of Young’s modulus (193 MPa for PCL, 378 MPa for PCL/Ti2 and 415 MPa for PCL/Zr2) were higher than those obtained from a previous theoretical modelling (144 MPa for PCL, 282 MPa for PCL/Ti2 and 310 MPa for PCL/Zr2). This correlation will be an important step for the evaluation of Young’s modulus, starting from the small punch test data. Full article
(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)
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Open AccessFeature PaperArticle Comparison of SF6 and CF4 Plasma Treatment for Surface Hydrophobization of PET Polymer
Materials 2018, 11(2), 311; https://doi.org/10.3390/ma11020311
Received: 20 January 2018 / Revised: 13 February 2018 / Accepted: 18 February 2018 / Published: 21 February 2018
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Abstract
The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission
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The fluorination of the polymer polyethylene terephthalate in plasma created from SF6 or CF4 gas at various pressures was investigated. The surface was analysed by X-ray photoelectron spectroscopy and water contact angle measurements, whereas the plasma was characterized by optical emission spectroscopy. The extent of the polymer surface fluorination was dependent on the pressure. Up to a threshold pressure, the amount of fluorine on the polymer surface and the surface hydrophobicity were similar, which was explained by the full dissociation of the SF6 and CF4 gases, leading to high concentrations of fluorine radicals in the plasma and thus causing the saturation of the polymer surface with fluorine functional groups. Above the threshold pressure, the amount of fluorine on the polymer surface significantly decreased, whereas the oxygen concentration increased, leading to the formation of the hydrophilic surface. This effect, which was more pronounced for the SF6 plasma, was explained by the electronegativity of both gases. Full article
(This article belongs to the Special Issue Surface Modification to Improve Properties of Materials)
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Open AccessArticle Research on the Transmission Characteristics of Air-Coupled Ultrasound in Double-Layered Bonded Structures
Materials 2018, 11(2), 310; https://doi.org/10.3390/ma11020310
Received: 28 January 2018 / Revised: 28 January 2018 / Accepted: 18 February 2018 / Published: 21 February 2018
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Abstract
The ultrasonic transmission spectrum in a double-layered bonded structure is related closely to its interfacial stiffness. Consequently, researching the regularity of the transmission spectrum is of significant interest in evaluating the integrity of the bonded structure. Based on the spring model and the
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The ultrasonic transmission spectrum in a double-layered bonded structure is related closely to its interfacial stiffness. Consequently, researching the regularity of the transmission spectrum is of significant interest in evaluating the integrity of the bonded structure. Based on the spring model and the potential function theory, a theoretical model is developed by the transfer matrix method to predict the transmission spectrum in a double-layered bonded structure. Some shift rules of the transmission peaks are obtained by numerical calculation of this model with different substrates. The results show that the resonant transmission peaks move towards a higher frequency with the increase of the normal interfacial stiffness, and each of them has different movement distances with the increasing interfacial stiffness. Indeed, it is also observed that the movement starting points of these peaks are at the specific frequency at which the thickness of either substrate plate equals an integral multiple of half a wavelength. The results from measuring the bonding specimens, which have different interfacial properties and different substrates in this experiment, are utilized to verify the theoretical analysis. Though the theory of “starting points” is not demonstrated effectively, the shift direction and distance exactly match with the result from the theoretical algorithm. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle An Innovative Approach to Control Steel Reinforcement Corrosion by Self-Healing
Materials 2018, 11(2), 309; https://doi.org/10.3390/ma11020309
Received: 29 January 2018 / Revised: 11 February 2018 / Accepted: 12 February 2018 / Published: 20 February 2018
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Abstract
The corrosion of reinforced steel, and subsequent reinforced concrete degradation, is a major concern for infrastructure durability. New materials with specific, tailor-made properties or the establishment of optimum construction regimes are among the many approaches to improving civil structure performance. Ideally, novel materials
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The corrosion of reinforced steel, and subsequent reinforced concrete degradation, is a major concern for infrastructure durability. New materials with specific, tailor-made properties or the establishment of optimum construction regimes are among the many approaches to improving civil structure performance. Ideally, novel materials would carry self-repairing or self-healing capacities, triggered in the event of detrimental influence and/or damage. Controlling or altering a material’s behavior at the nano-level would result in traditional materials with radically enhanced properties. Nevertheless, nanotechnology applications are still rare in construction, and would break new ground in engineering practice. An approach to controlling the corrosion-related degradation of reinforced concrete was designed as a synergetic action of electrochemistry, cement chemistry and nanotechnology. This contribution presents the concept of the approach, namely to simultaneously achieve steel corrosion resistance and improved bulk matrix properties. The technical background and challenges for the application of polymeric nanomaterials in the field are briefly outlined in view of this concept, which has the added value of self-healing. The credibility of the approach is discussed with reference to previously reported outcomes, and is illustrated via the results of the steel electrochemical responses and microscopic evaluations of the discussed materials. Full article
(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)
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Open AccessArticle Layup Configuration Effect on Notch Residual Strength in Composite Laminates
Materials 2018, 11(2), 308; https://doi.org/10.3390/ma11020308
Received: 30 January 2018 / Revised: 14 February 2018 / Accepted: 15 February 2018 / Published: 20 February 2018
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Abstract
The current trend shows an increasing demand for composites due to their high stiffness to weight ratio and the recent progress in manufacturing and cost reduction of composites. To combine high strength and stiffness in a cost-effective way, composites are often joined with
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The current trend shows an increasing demand for composites due to their high stiffness to weight ratio and the recent progress in manufacturing and cost reduction of composites. To combine high strength and stiffness in a cost-effective way, composites are often joined with steel or aluminum. However, joining of thermoset composite materials is challenging because circular holes are often used to join them with their metal counterparts. These design based circular holes induce high stress concentration around the hole. The purpose of this paper is to focus on layup configuration and its impact on notch stress distribution. To ensure high quality and uniformity, the holes were machined by a 5 kW continuous wave (cw) CO2 laser. The stress distribution was evaluated and compared by using finite element analysis and Lekhnitskii’s equations. For further understanding, the notch strength of the laminates was compared and strain distributions were analyzed using the digital image correlation technique. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessFeature PaperArticle TiO2@PEI-Grafted-MWCNTs Hybrids Nanocomposites Catalysts for CO2 Photoreduction
Materials 2018, 11(2), 307; https://doi.org/10.3390/ma11020307
Received: 19 January 2018 / Revised: 13 February 2018 / Accepted: 13 February 2018 / Published: 20 February 2018
Cited by 1 | PDF Full-text (5338 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Anatase (TiO2) and multiwalled carbon nanotubes bearing polyethylenimine (PEI) anchored on their surface were hybridized in different proportions according to a sol-gel method. The resulting nanocomposites (TiO2@PEI-MWCNTs), characterized by BET, XRD, XPS, SEM, and UV techniques, were found efficient
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Anatase (TiO2) and multiwalled carbon nanotubes bearing polyethylenimine (PEI) anchored on their surface were hybridized in different proportions according to a sol-gel method. The resulting nanocomposites (TiO2@PEI-MWCNTs), characterized by BET, XRD, XPS, SEM, and UV techniques, were found efficient catalysts for CO2 photoreduction into formic and acetic acids in water suspension and under visible light irradiation. PEI-grafted nanotubes co-catalysts are believed to act as CO2 activators by forming a carbamate intermediate allowing to accomplish the first example in the literature of polyamines/nanotubes/TiO2 mediated CO2 photoreduction to carboxylic acids. Full article
(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)
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Open AccessArticle Computational and Experimental Mechanical Modelling of a Composite Grouted Splice Sleeve Connector System
Materials 2018, 11(2), 306; https://doi.org/10.3390/ma11020306
Received: 19 January 2018 / Revised: 14 February 2018 / Accepted: 15 February 2018 / Published: 20 February 2018
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Abstract
Owing to its controllable tolerance, simple operation and no need for welding at construction site, the composite system involving grouted cement material, steel material and ductile iron material is widely used as grouted splice sleeve (GSS) connector for connecting precast concrete structures. However,
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Owing to its controllable tolerance, simple operation and no need for welding at construction site, the composite system involving grouted cement material, steel material and ductile iron material is widely used as grouted splice sleeve (GSS) connector for connecting precast concrete structures. However, the current design recommendations for such a composite connection system do not accurately account for its material nonlinearity behavior. In the present study, a three-dimensional nonlinear finite element model of a GSS connector is developed by considering the nonlinear material behavior of each component to fully investigate its mechanical performance under axial tension. To validate the proposed computational model and demonstrate the nonlinear response of the GSS connector, the pullout experimental test of two engineering specimens is carried out under monotonic tensile load, and a good agreement between the numerical and experimental test results is observed. Then, the sensitivity analysis of some controlling material properties and geometrical parameters is performed using the validated computational model to further understand the performance of such a composite structure in load carrying capacity and ductility of the connections to meet the rapid engineering applications of precast concrete structures. Full article
(This article belongs to the Special Issue Modeling and Simulation of Advanced Composite Materials)
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Open AccessArticle A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl Alloy
Materials 2018, 11(2), 305; https://doi.org/10.3390/ma11020305
Received: 19 January 2018 / Revised: 7 February 2018 / Accepted: 12 February 2018 / Published: 20 February 2018
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Abstract
In this work, plastic deformation was locally introduced at room temperature by nanoindentation on a γ-TiAl-based alloy. Comprehensive analyses of microstructures were performed before and after deformation. In particular, the Burgers vectors, the line directions, and the mechanical twinning systems were studied via
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In this work, plastic deformation was locally introduced at room temperature by nanoindentation on a γ-TiAl-based alloy. Comprehensive analyses of microstructures were performed before and after deformation. In particular, the Burgers vectors, the line directions, and the mechanical twinning systems were studied via accurate electron channeling contrast imaging. Accommodation of the deformation are reported and a scenario is proposed. All features help to explain the poor ductility of the TiAl-based alloys at room temperature. Full article
(This article belongs to the Special Issue Design of Alloy Metals for Low-Mass Structures)
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Open AccessArticle Tunable Bandgap and Optical Properties of Black Phosphorene Nanotubes
Materials 2018, 11(2), 304; https://doi.org/10.3390/ma11020304
Received: 12 January 2018 / Revised: 6 February 2018 / Accepted: 9 February 2018 / Published: 19 February 2018
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Abstract
Black phosphorus (BP), a new two-dimensional material, has been the focus of scientists’ attention. BP nanotubes have potential in the field of optoelectronics due to their low-dimensional effects. In this work, the bending strain energy, electronic structure, and optical properties of BP nanotubes
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Black phosphorus (BP), a new two-dimensional material, has been the focus of scientists’ attention. BP nanotubes have potential in the field of optoelectronics due to their low-dimensional effects. In this work, the bending strain energy, electronic structure, and optical properties of BP nanotubes were investigated by using the first-principles method based on density functional theory. The results show that these properties are closely related to the rolling direction and radius of the BP nanotube. All the calculated BP nanotube properties show direct bandgaps, and the BP nanotubes with the same rolling direction express a monotone increasing trend in the value of bandgap with a decrease in radius, which is a stacking effect of the compression strain on the inner atoms and the tension strain on the outer atoms. The bending strain energy of the zigzag phosphorene nanotubes (zPNTs) is higher than that of armchair phosphorene nanotubes (aPNT) with the same radius of curvature due to the anisotropy of the BP’s structure. The imaginary part of the dielectric function, the absorption range, reflectivity, and the imaginary part of the refractive index of aPNTs have a wider range than those of zPNTs, with higher values overall. As a result, tunable BP nanotubes are suitable for optoelectronic devices, such as lasers and diodes, which function in the infrared and ultra-violet regions, and for solar cells and photocatalysis. Full article
(This article belongs to the Section Advanced Nanomaterials)
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Open AccessArticle Synthesis, Structural Property, Photophysical Property, Photocatalytic Property of Novel ZnBiErO4 under Visible Light Irradiation
Materials 2018, 11(2), 303; https://doi.org/10.3390/ma11020303
Received: 29 December 2017 / Revised: 26 January 2018 / Accepted: 30 January 2018 / Published: 18 February 2018
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Abstract
A novel photocatalyst ZnBiErO4 was firstly synthesized by solid-state reaction method and its structural and photocatalytic properties were analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance. The results demonstrated that ZnBiErO4 crystallized with tetragonal crystal
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A novel photocatalyst ZnBiErO4 was firstly synthesized by solid-state reaction method and its structural and photocatalytic properties were analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance. The results demonstrated that ZnBiErO4 crystallized with tetragonal crystal structure with space group I41/A. The lattice parameters for ZnBiErO4 were proved to be a = b = 10.255738 Å and c = 9.938888 Å. The band gap of ZnBiErO4 was estimated to be about 1.69 eV. Compared with nitrogen doped TiO2, ZnBiErO4 showed excellent photocatalytic activities for degrading methyl blue during visible light irradiation. The photocatalytic degradation of methyl blue with ZnBiErO4 or N-doped TiO2 as catalyst followed the first-order reaction kinetics. Moreover, the apparent first-order rate constant of ZnBiErO4 or N-doped TiO2 was 0.01607 min−1 or 0.00435 min−1. The reduction of total organic carbon, formation of inorganic products, such as SO42− and NO3 and the evolution of CO2 revealed the continuous mineralization of methyl blue during the photocatalytic process. ZnBiErO4 photocatalyst had great potential to purify textile industry wastewater. Full article
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Open AccessFeature PaperReview Nanogels for Pharmaceutical and Biomedical Applications and Their Fabrication Using 3D Printing Technologies
Materials 2018, 11(2), 302; https://doi.org/10.3390/ma11020302
Received: 11 January 2018 / Revised: 13 February 2018 / Accepted: 14 February 2018 / Published: 16 February 2018
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Abstract
Nanogels are hydrogels formed by connecting nanoscopic micelles dispersed in an aqueous medium, which give an opportunity for incorporating hydrophilic payloads to the exterior of the micellar networks and hydrophobic payloads in the core of the micelles. Biomedical and pharmaceutical applications of nanogels
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Nanogels are hydrogels formed by connecting nanoscopic micelles dispersed in an aqueous medium, which give an opportunity for incorporating hydrophilic payloads to the exterior of the micellar networks and hydrophobic payloads in the core of the micelles. Biomedical and pharmaceutical applications of nanogels have been explored for tissue regeneration, wound healing, surgical device, implantation, and peroral, rectal, vaginal, ocular, and transdermal drug delivery. Although it is still in the early stages of development, due to the increasing demands of precise nanogel production to be utilized for personalized medicine, biomedical applications, and specialized drug delivery, 3D printing has been explored in the past few years and is believed to be one of the most precise, efficient, inexpensive, customizable, and convenient manufacturing techniques for nanogel production. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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Open AccessArticle Highly Efficient Intracellular Protein Delivery by Cationic Polyethyleneimine-Modified Gelatin Nanoparticles
Materials 2018, 11(2), 301; https://doi.org/10.3390/ma11020301
Received: 26 January 2018 / Revised: 13 February 2018 / Accepted: 13 February 2018 / Published: 15 February 2018
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Abstract
Intracellular protein delivery may provide a safe and non-genome integrated strategy for targeting abnormal or specific cells for applications in cell reprogramming therapy. Thus, highly efficient intracellular functional protein delivery would be beneficial for protein drug discovery. In this study, we generated a
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Intracellular protein delivery may provide a safe and non-genome integrated strategy for targeting abnormal or specific cells for applications in cell reprogramming therapy. Thus, highly efficient intracellular functional protein delivery would be beneficial for protein drug discovery. In this study, we generated a cationic polyethyleneimine (PEI)-modified gelatin nanoparticle and evaluated its intracellular protein delivery ability in vitro and in vivo. The experimental results showed that the PEI-modified gelatin nanoparticle had a zeta potential of approximately +60 mV and the particle size was approximately 135 nm. The particle was stable at different biological pH values and temperatures and high protein loading efficiency was observed. The fluorescent image results revealed that large numbers of particles were taken up into the mammalian cells and escaped from the endosomes into the cytoplasm. In a mouse C26 cell-xenograft cancer model, particles accumulated in cancer cells. In conclusion, the PEI-modified gelatin particle may provide a biodegradable and highly efficient protein delivery system for use in regenerative medicine and cancer therapy. Full article
(This article belongs to the Section Biomaterials)
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