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Materials, Volume 8, Issue 9 (September 2015)

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Open AccessArticle Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors
Materials 2015, 8(9), 6570-6588; https://doi.org/10.3390/ma8095323
Received: 31 August 2015 / Accepted: 21 September 2015 / Published: 23 September 2015
Cited by 7 | PDF Full-text (2102 KB) | HTML Full-text | XML Full-text
Abstract
In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads
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In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO2 and NH3, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
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Open AccessArticle Influence of Screw Length and Bone Thickness on the Stability of Temporary Implants
Materials 2015, 8(9), 6558-6569; https://doi.org/10.3390/ma8095322
Received: 17 July 2015 / Accepted: 16 September 2015 / Published: 23 September 2015
Cited by 2 | PDF Full-text (1940 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this work was to study the influence of screw length and bone thickness on the stability of temporary implants. A total of 96 self-drilling temporary screws with two different lengths were inserted into polyurethane blocks (n = 66), bovine femurs
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The purpose of this work was to study the influence of screw length and bone thickness on the stability of temporary implants. A total of 96 self-drilling temporary screws with two different lengths were inserted into polyurethane blocks (n = 66), bovine femurs (n = 18) and rabbit tibia (n = 12) with different cortical thicknesses (1 to 8 mm). Screws insertion in polyurethane blocks was assisted by a universal testing machine, torque peaks were collected by a digital torquemeter and bone thickness was monitored by micro-CT. The results showed that the insertion torque was significantly increased with the thickness of cortical bone from polyurethane (p < 0.0001), bovine (p = 0.0035) and rabbit (p < 0.05) sources. Cancellous bone improved significantly the mechanical implant stability. Insertion torque and insertion strength was successfully moduled by equations, based on the cortical/cancellous bone behavior. Based on the results, insertion torque and bone strength can be estimate in order to prevent failure of the cortical layer during temporary screw placement. The stability provided by a cortical thickness of 2 or 1 mm coupled to cancellous bone was deemed sufficient for temporary implants stability. Full article
(This article belongs to the Section Biomaterials)
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Open AccessCommunication Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates
Materials 2015, 8(9), 6543-6557; https://doi.org/10.3390/ma8095321
Received: 19 August 2015 / Accepted: 16 September 2015 / Published: 23 September 2015
Cited by 8 | PDF Full-text (649 KB) | HTML Full-text | XML Full-text
Abstract
Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester’s material quality; Cupriavidus necator was applied as microbial production strain.
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Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester’s material quality; Cupriavidus necator was applied as microbial production strain. For proof of concept, pre-experiments were carried out on a shake flask scale using different mixtures of glucose and LW as carbon source. The results indicate that LW definitely acts as a 3HV precursor, but, at the same time, displays toxic effects on C. necator at concentrations exceeding 10 g/L. Based on these findings, PHA biosynthesis under controlled conditions was performed using a fed-batch feeding regime on a bioreactor scale. As major outcome, a poly(3HB-co-0.8%-3HV) copolyester was obtained displaying a desired high molar mass of Mw = 5.39 × 105 g/mol at low molar-mass dispersity (ĐM of 1.53), a degree of crystallinity (Xc) of 62.1%, and melting temperature Tm (176.3 °C) slightly lower than values reported for poly([R]-3-hydroxybutyrate) (PHB) homopolyester produced by C. necator; thus, the produced biopolyester is expected to be more suitable for polymer processing purposes. Full article
(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)
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Open AccessArticle Engineered Heusler Ferrimagnets with a Large Perpendicular Magnetic Anisotropy
Materials 2015, 8(9), 6531-6542; https://doi.org/10.3390/ma8095320
Received: 6 August 2015 / Revised: 4 September 2015 / Accepted: 15 September 2015 / Published: 22 September 2015
Cited by 1 | PDF Full-text (1094 KB) | HTML Full-text | XML Full-text
Abstract
Synthetic perpendicular magnetic anisotropy (PMA) ferrimagnets consisting of 30-nm-thick D022-MnGa and Co2MnSi (CMS) cubic Heusler alloys with different thicknesses of 1, 3, 5, 10 and 20 nm, buffered and capped with a Cr film, are successfully grown epitaxially on
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Synthetic perpendicular magnetic anisotropy (PMA) ferrimagnets consisting of 30-nm-thick D022-MnGa and Co2MnSi (CMS) cubic Heusler alloys with different thicknesses of 1, 3, 5, 10 and 20 nm, buffered and capped with a Cr film, are successfully grown epitaxially on MgO substrate. Two series samples with and without post annealing at 400 °C are fabricated. The (002) peak of the cubic L21 structure of CMS films on the MnGa layer is observed, even for the 3-nm-thick CMS film for both un-annealed and annealed samples. The smaller remnant magnetization and larger switching field values of CMS (1–20 nm)/MnGa (30 nm) bilayers compared with 30-nm-thick MnGa indicates antiferromagnetic (AFM) interfacial exchange coupling (Jex) between MnGa and CMS films for both un-annealed and annealed samples. The critical thickness of the CMS film for observing PMA with AFM coupling in the CMS/MnGa bilayer is less than 10 nm, which is relatively large compared to previous studies. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
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Open AccessArticle Feasibility Studies of Palm Oil Mill Waste Aggregates for the Construction Industry
Materials 2015, 8(9), 6508-6530; https://doi.org/10.3390/ma8095319
Received: 28 July 2015 / Revised: 10 September 2015 / Accepted: 15 September 2015 / Published: 22 September 2015
Cited by 17 | PDF Full-text (6693 KB) | HTML Full-text | XML Full-text
Abstract
The agricultural industry in Malaysia has grown rapidly over the years. Palm oil clinker (POC) is a byproduct obtained from the palm oil industry. Its lightweight properties allows for its utilization as an aggregate, while in powder form as a filler material in
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The agricultural industry in Malaysia has grown rapidly over the years. Palm oil clinker (POC) is a byproduct obtained from the palm oil industry. Its lightweight properties allows for its utilization as an aggregate, while in powder form as a filler material in concrete. POC specimens obtained throughout each state in Malaysia were investigated to evaluate the physical, chemical, and microstructure characteristics. Variations between each state were determined and their possible contributory factors were assessed. POC were incorporated as a replacement material for aggregates and their engineering characteristics were ascertained. Almost 7% of density was reduced with the introduction of POC as aggregates. A sustainability assessment was made through greenhouse gas emission (GHG) and cost factor analyses to determine the contribution of the addition of POC to the construction industry. Addition of POC helps to lower the GHG emission by 9.6% compared to control specimens. By channeling this waste into the construction industry, an efficient waste-management system can be promoted; thus, creating a cleaner environment. This study is also expected to offer some guides and directions for upcoming research works on the incorporation of POC. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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Open AccessArticle Study on Platinum Coating Depth in Focused Ion Beam Diamond Cutting Tool Milling and Methods for Removing Platinum Layer
Materials 2015, 8(9), 6498-6507; https://doi.org/10.3390/ma8095317
Received: 29 July 2015 / Revised: 3 September 2015 / Accepted: 15 September 2015 / Published: 22 September 2015
Cited by 1 | PDF Full-text (1603 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, nanomachining has attracted increasing attention in advanced manufacturing science and technologies as a value-added processes to control material structures, components, devices, and nanoscale systems. To make sub-micro patterns on these products, micro/nanoscale single-crystal diamond cutting tools are essential. Popular non-contact
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In recent years, nanomachining has attracted increasing attention in advanced manufacturing science and technologies as a value-added processes to control material structures, components, devices, and nanoscale systems. To make sub-micro patterns on these products, micro/nanoscale single-crystal diamond cutting tools are essential. Popular non-contact methods for the macro/micro processing of diamond composites are pulsed laser ablation (PLA) and electric discharge machining (EDM). However, for manufacturing nanoscale diamond tools, these machining methods are not appropriate. Despite diamond’s extreme physical properties, diamond can be micro/nano machined relatively easily using a focused ion beam (FIB) technique. In the FIB milling process, the surface properties of the diamond cutting tool is affected by the amorphous damage layer caused by the FIB gallium ion collision and implantation and these influence the diamond cutting tool edge sharpness and increase the processing procedures. To protect the diamond substrate, a protection layer—platinum (Pt) coating is essential in diamond FIB milling. In this study, the depth of Pt coating layer which could decrease process-induced damage during FIB fabrication is investigated, along with methods for removing the Pt coating layer on diamond tools. The optimum Pt coating depth has been confirmed, which is very important for maintaining cutting tool edge sharpness and decreasing processing procedures. The ultra-precision grinding method and etching with aqua regia method have been investigated for removing the Pt coating layer. Experimental results show that when the diamond cutting tool width is bigger than 500 nm, ultra-precision grinding method is appropriate for removing Pt coating layer on diamond tool. However, the ultra-precision grinding method is not recommended for removing the Pt coating layer when the cutting tool width is smaller than 500 nm, because the possibility that the diamond cutting tool is damaged by the grinding process will be increased. Despite the etching method requiring more procedures to remove the Pt coating layer after FIB milling, it is a feasible method for diamond tools with under 500 nm width. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
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Open AccessArticle Characterization of Platinum Nanoparticles Deposited on Functionalized Graphene Sheets
Materials 2015, 8(9), 6484-6497; https://doi.org/10.3390/ma8095318
Received: 18 August 2015 / Revised: 11 September 2015 / Accepted: 17 September 2015 / Published: 21 September 2015
Cited by 6 | PDF Full-text (3370 KB) | HTML Full-text | XML Full-text
Abstract
Due to its special electronic and ballistic transport properties, graphene has attracted much interest from researchers. In this study, platinum (Pt) nanoparticles were deposited on oxidized graphene sheets (cG). The graphene sheets were applied to overcome the corrosion problems of carbon black at
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Due to its special electronic and ballistic transport properties, graphene has attracted much interest from researchers. In this study, platinum (Pt) nanoparticles were deposited on oxidized graphene sheets (cG). The graphene sheets were applied to overcome the corrosion problems of carbon black at operating conditions of proton exchange membrane fuel cells. To enhance the interfacial interactions between the graphene sheets and the Pt nanoparticles, the oxygen-containing functional groups were introduced onto the surface of graphene sheets. The results showed the Pt nanoparticles were uniformly dispersed on the surface of graphene sheets with a mean Pt particle size of 2.08 nm. The Pt nanoparticles deposited on graphene sheets exhibited better crystallinity and higher oxygen resistance. The metal Pt was the predominant Pt chemical state on Pt/cG (60.4%). The results from the cyclic voltammetry analysis showed the value of the electrochemical surface area (ECSA) was 88 m2/g (Pt/cG), much higher than that of Pt/C (46 m2/g). The long-term test illustrated the degradation in ECSA exhibited the order of Pt/C (33%) > Pt/cG (7%). The values of the utilization efficiency were calculated to be 64% for Pt/cG and 32% for Pt/C. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
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Open AccessCorrection Jood, P. and Ohta, M. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides. Materials 2015, 8, 1124–1149
Materials 2015, 8(9), 6482-6483; https://doi.org/10.3390/ma8095315
Received: 8 September 2015 / Accepted: 8 September 2015 / Published: 21 September 2015
Cited by 1 | PDF Full-text (84 KB) | HTML Full-text | XML Full-text
Abstract
The authors wish to make the following corrections to this paper [1]. [...] Full article
(This article belongs to the Section Energy Materials)
Open AccessArticle Investigation of the Optoelectronic Properties of Ti-doped Indium Tin Oxide Thin Film
Materials 2015, 8(9), 6471-6481; https://doi.org/10.3390/ma8095316
Received: 3 July 2015 / Revised: 15 August 2015 / Accepted: 10 September 2015 / Published: 21 September 2015
Cited by 6 | PDF Full-text (1392 KB) | HTML Full-text | XML Full-text
Abstract
: In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO) thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The
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: In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO) thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The Ti-doped ITO thin films exhibited superior thin-film resistivity (1.5 × 104 Ω/cm), carrier concentration (4.1 × 1021 cm3), carrier mobility (10 cm2/Vs), and mean visible-light transmittance (90%) at wavelengths of 400–800 nm at a deposition temperature of 400 °C. The superior carrier concentration of the Ti-doped ITO alloys (>1021 cm3) with a high figure of merit (81.1 × 1031) demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Electrochemical Behavior of Al-B4C Metal Matrix Composites in NaCl Solution
Materials 2015, 8(9), 6455-6470; https://doi.org/10.3390/ma8095314
Received: 21 August 2015 / Revised: 13 September 2015 / Accepted: 15 September 2015 / Published: 21 September 2015
Cited by 8 | PDF Full-text (3741 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum based metal matrix composites (MMCs) have received considerable attention in the automotive, aerospace and nuclear industries. One of the main challenges using Al-based MMCs is the influence of the reinforcement particles on the corrosion resistance. In the present study, the corrosion behavior
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Aluminum based metal matrix composites (MMCs) have received considerable attention in the automotive, aerospace and nuclear industries. One of the main challenges using Al-based MMCs is the influence of the reinforcement particles on the corrosion resistance. In the present study, the corrosion behavior of Al-B4C MMCs in a 3.5 wt.% NaCl solution were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. Results indicated that the corrosion resistance of the composites decreased when increasing the B4C volume fraction. Al-B4C composite was susceptible to pitting corrosion and two types of pits were observed on the composite surface. The corrosion mechanism of the composite in the NaCl solution was primarily controlled by oxygen diffusion in the solution. In addition, the galvanic couples that formed between Al matrix and B4C particles could also be responsible for the lower corrosion resistance of the composites. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Nanocrystalline BaSnO3 as an Alternative Gas Sensor Material: Surface Reactivity and High Sensitivity to SO2
Materials 2015, 8(9), 6437-6454; https://doi.org/10.3390/ma8095311
Received: 14 July 2015 / Revised: 31 August 2015 / Accepted: 11 September 2015 / Published: 18 September 2015
Cited by 14 | PDF Full-text (2655 KB) | HTML Full-text | XML Full-text
Abstract
Nanocrystalline perovskite-type BaSnO3 was obtained via microwave-assisted hydrothermal route followed by annealing at variable temperature. The samples composition and microstructure were characterized. Particle size of 18–23 nm was unaffected by heat treatment at 275–700 °C. Materials DC-conduction was measured at variable temperature
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Nanocrystalline perovskite-type BaSnO3 was obtained via microwave-assisted hydrothermal route followed by annealing at variable temperature. The samples composition and microstructure were characterized. Particle size of 18–23 nm was unaffected by heat treatment at 275–700 °C. Materials DC-conduction was measured at variable temperature and oxygen concentration. Barium stannate exhibited n-type semiconductor behavior at 150–450 °C with activation energy being dependent on the materials annealing temperature. Predominant ionosorbed oxygen species types were estimated. They were shown to change from molecular to atomic species on increasing temperature. Comparative test of sensor response to various inorganic target gases was performed using nanocrystalline SnO2-based sensors as reference ones. Despite one order of magnitude smaller surface area, BaSnO3 displayed higher sensitivity to SO2 in comparison with SnO2. DRIFT spectroscopy revealed distinct interaction routes of the oxides surfaces with SO2. Barium-promoted sulfate formation favoring target molecules oxidation was found responsible for the increased BaSnO3 sensitivity to ppm-range concentrations of SO2 in air. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
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Open AccessArticle A Comparative Study of the Sintering Behavior of Pure and Manganese-Substituted Hydroxyapatite
Materials 2015, 8(9), 6419-6436; https://doi.org/10.3390/ma8095308
Received: 12 July 2015 / Revised: 25 August 2015 / Accepted: 14 September 2015 / Published: 18 September 2015
Cited by 4 | PDF Full-text (4950 KB) | HTML Full-text | XML Full-text
Abstract
Hydroxyapatite (HA) is a widely studied biomaterial for its similar chemical composition to bone and its osteoconductive properties. The crystal structure of HA is flexible, allowing for a wide range of substitutions which can alter bioactivity, biodegradation, and mechanical properties of the substituted
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Hydroxyapatite (HA) is a widely studied biomaterial for its similar chemical composition to bone and its osteoconductive properties. The crystal structure of HA is flexible, allowing for a wide range of substitutions which can alter bioactivity, biodegradation, and mechanical properties of the substituted apatite. The thermal stability of a substituted apatite is an indication of its biodegradation in vivo. In this study, we investigated the thermal stability and mechanical properties of manganese-substituted hydroxyapatite (MnHA) as it is reported that manganese can enhance cell attachment compared to pure HA. Pure HA and MnHA pellets were sintered over the following temperature ranges: 900 to 1300 °C and 700 to 1300 °C respectively. The sintered pellets were characterized via density measurements, mechanical testing, X-ray diffraction, and field emission electron microscopy. It was found that MnHA was less stable than HA decomposing around 800 °C compared to 1200 °C for HA. The flexural strength of MnHA was weaker than HA due to the decomposition of MnHA at a significantly lower temperature of 800 °C compared to 1100 °C for HA. The low thermal stability of MnHA suggests that a faster in vivo dissolution rate compared to pure HA is expected. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Development of Chitosan/Bacterial Cellulose Composite Films Containing Nanodiamonds as a Potential Flexible Platform for Wound Dressing
Materials 2015, 8(9), 6401-6418; https://doi.org/10.3390/ma8095309
Received: 6 July 2015 / Revised: 29 August 2015 / Accepted: 3 September 2015 / Published: 18 September 2015
Cited by 20 | PDF Full-text (6286 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Chitosan/bacterial cellulose composite films containing diamond nanoparticles (NDs) with potential application as wound dressing are introduced. Microstructural studies show that NDs are uniformly dispersed in the matrix, although slight agglomeration at concentrations above 2 wt % is seen. Fourier transform infrared spectroscopy reveals
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Chitosan/bacterial cellulose composite films containing diamond nanoparticles (NDs) with potential application as wound dressing are introduced. Microstructural studies show that NDs are uniformly dispersed in the matrix, although slight agglomeration at concentrations above 2 wt % is seen. Fourier transform infrared spectroscopy reveals formation of hydrogen bonds between NDs and the polymer matrix. X-ray diffraction analysis indicates reduced crystallinity of the polymer matrix in the presence of NDs. Approximately 3.5-fold increase in the elastic modulus of the composite film is obtained by the addition of 2 wt % NDs. The results of colorimetric analysis show that the composite films are transparent but turn to gray-like and semitransparent at high ND concentrations. Additionally, a decrease in highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) gap is also seen, which results in a red shift and higher absorption intensity towards the visible region. Mitochondrial activity assay using L929 fibroblast cells shows that the nanocomposite films are biocompatible (>90%) after 24 h incubation. Multiple lamellapodia and cell-cell interaction are shown. The results suggest that the developed films can potentially be used as a flexible platform for wound dressing. Full article
(This article belongs to the Special Issue Biobased Nanocomposite Functional Materials)
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Open AccessArticle Electroactive Shape Memory Property of a Cu-decorated CNT Dispersed PLA/ESO Nanocomposite
Materials 2015, 8(9), 6391-6400; https://doi.org/10.3390/ma8095313
Received: 20 June 2015 / Revised: 21 August 2015 / Accepted: 14 September 2015 / Published: 18 September 2015
Cited by 6 | PDF Full-text (1069 KB) | HTML Full-text | XML Full-text
Abstract
Shape memory polymer (SMP) nanocomposites with a fast electro-actuation speed were prepared by dispersing Cu-decorated carbon nanotubes (CNTs) (Cu-CNTs, 1 wt %, 2 wt %, and 3 wt %) in a polylactic acid (PLA)/epoxidized soybean oil (ESO) blend matrix. The shape
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Shape memory polymer (SMP) nanocomposites with a fast electro-actuation speed were prepared by dispersing Cu-decorated carbon nanotubes (CNTs) (Cu-CNTs, 1 wt %, 2 wt %, and 3 wt %) in a polylactic acid (PLA)/epoxidized soybean oil (ESO) blend matrix. The shape memory effect (SME) induced by an electrical current was investigated by a fold-deploy “U”-shape bending test. In addition, the Cu-CNT dispersed PLA/ESO nanocomposite was characterized by atomic force microscopy (AFM), dynamic mechanical analysis (DMA) and tensile and electrical measurements. The results demonstrated that the SME was dependent on the Cu-CNT content in the nanocomposites. When comparing the SMEs of the nanocomposite specimens with different Cu-CNT contents, the 2 wt % Cu-CNT dispersed system exhibited a shape recovery as high as 98% within 35 s due to its higher electrical conductivity that results from uniform Cu-CNT dispersion. However, the nanocomposites that contained 1 wt % and 3 wt % Cu-CNTs required 75 s and 63 s, respectively, to reach a maximum recovery level. In addition, the specimens exhibited better mechanical properties after the addition of Cu-CNTs. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Plasma Enhanced Complete Oxidation of Ultrathin Epitaxial Praseodymia Films on Si(111)
Materials 2015, 8(9), 6379-6390; https://doi.org/10.3390/ma8095312
Received: 29 July 2015 / Revised: 10 September 2015 / Accepted: 14 September 2015 / Published: 18 September 2015
PDF Full-text (707 KB) | HTML Full-text | XML Full-text
Abstract
Praseodymia films have been exposed to oxygen plasma at room temperature after deposition on Si(111) via molecular beam epitaxy. Different parameters as film thickness, exposure time and flux during plasma treatment have been varied to study their influence on the oxygen plasma oxidation
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Praseodymia films have been exposed to oxygen plasma at room temperature after deposition on Si(111) via molecular beam epitaxy. Different parameters as film thickness, exposure time and flux during plasma treatment have been varied to study their influence on the oxygen plasma oxidation process. The surface near regions have been investigated by means of X-ray photoelectron spectroscopy showing that the plasma treatment transforms the stoichiometry of the films from Pr2O3 to PrO2. Closer inspection of the bulk properties of the films by means of synchrotron radiation based X-ray reflectometry and diffraction confirms this transformation if the films are thicker than some critical thickness of 6 nm. The layer distance of these films is extremely small verifying the completeness of the plasma oxidation process. Thinner films, however, cannot be transformed completely. For all films, less oxidized very thin interlayers are detected by these experimental techniques. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
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