Materials

2102 KiB

Open AccessArticle

Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors

by Konrad Maier, Andreas Helwig, Gerhard Müller, Pascal Hille and Martin Eickhoff

Materials 2015, 8(9), 6570-6588; https://doi.org/10.3390/ma8095323 - 23 Sep 2015

Cited by 25 | Viewed by 11695

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 [...] Read more.

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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1940 KiB

Open AccessArticle

Influence of Screw Length and Bone Thickness on the Stability of Temporary Implants

by Daniel Jogaib Fernandes, Carlos Nelson Elias and Antônio Carlos de Oliveira Ruellas

Materials 2015, 8(9), 6558-6569; https://doi.org/10.3390/ma8095322 - 23 Sep 2015

Cited by 11 | Viewed by 5664

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 [...] Read more.

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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649 KiB

Open AccessCommunication

Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates

by Martin Koller, Miguel Miranda de Sousa Dias, Alejandra Rodríguez-Contreras, Matjaž Kunaver, Ema Žagar, Andrej Kržan and Gerhart Braunegg

Materials 2015, 8(9), 6543-6557; https://doi.org/10.3390/ma8095321 - 23 Sep 2015

Cited by 40 | Viewed by 6555

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. [...] Read more.

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 M_w = 5.39 × 10⁵ g/mol at low molar-mass dispersity (Đ_M of 1.53), a degree of crystallinity (X_c) of 62.1%, and melting temperature T_m (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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1094 KiB

Open AccessArticle

Engineered Heusler Ferrimagnets with a Large Perpendicular Magnetic Anisotropy

by Reza Ranjbar, Kazuya Suzuki, Atsushi Sugihara, Terunobu Miyazaki, Yasuo Ando and Shigemi Mizukami

Materials 2015, 8(9), 6531-6542; https://doi.org/10.3390/ma8095320 - 22 Sep 2015

Cited by 6 | Viewed by 4972

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 [...] Read more.

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 (J_ex) 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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6693 KiB

Open AccessArticle

Feasibility Studies of Palm Oil Mill Waste Aggregates for the Construction Industry

by Jegathish Kanadasan, Auni Filzah Ahmad Fauzi, Hashim Abdul Razak, Paramananthan Selliah, Vijaya Subramaniam and Sumiani Yusoff

Materials 2015, 8(9), 6508-6530; https://doi.org/10.3390/ma8095319 - 22 Sep 2015

Cited by 53 | Viewed by 8493

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 [...] Read more.

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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1603 KiB

Open AccessArticle

Study on Platinum Coating Depth in Focused Ion Beam Diamond Cutting Tool Milling and Methods for Removing Platinum Layer

by Woong Kirl Choi and Seung Yub Baek

Materials 2015, 8(9), 6498-6507; https://doi.org/10.3390/ma8095317 - 22 Sep 2015

Cited by 4 | Viewed by 6904

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 [...] Read more.

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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3370 KiB

Open AccessArticle

Characterization of Platinum Nanoparticles Deposited on Functionalized Graphene Sheets

by Yu-Chun Chiang, Chia-Chun Liang and Chun-Ping Chung

Materials 2015, 8(9), 6484-6497; https://doi.org/10.3390/ma8095318 - 21 Sep 2015

Cited by 30 | Viewed by 10190

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 [...] Read more.

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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84 KiB

Open AccessCorrection

Jood, P. and Ohta, M. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides. Materials 2015, 8, 1124–1149

by Priyanka Jood and Michihiro Ohta

Materials 2015, 8(9), 6482-6483; https://doi.org/10.3390/ma8095315 - 21 Sep 2015

Cited by 4 | Viewed by 3810

Abstract

The authors wish to make the following corrections to this paper [1]. [...] Full article

(This article belongs to the Section Energy Materials)

1392 KiB

Open AccessArticle

Investigation of the Optoelectronic Properties of Ti-doped Indium Tin Oxide Thin Film

by Nen-Wen Pu, Wei-Sheng Liu, Huai-Ming Cheng, Hung-Chun Hu, Wei-Ting Hsieh, Hau-Wei Yu and Shih-Chang Liang

Materials 2015, 8(9), 6471-6481; https://doi.org/10.3390/ma8095316 - 21 Sep 2015

Cited by 26 | Viewed by 7545

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 [...] Read more.

: 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 × 10⁻⁴ Ω/cm), carrier concentration (4.1 × 10²¹ cm⁻³), 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 cm⁻³) with a high figure of merit (81.1 × 10⁻³ Ω⁻¹) demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices. Full article

(This article belongs to the Section Advanced Materials Characterization)

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3741 KiB

Open AccessArticle

Electrochemical Behavior of Al-B₄C Metal Matrix Composites in NaCl Solution

by Yu-Mei Han and X.-Grant Chen

Materials 2015, 8(9), 6455-6470; https://doi.org/10.3390/ma8095314 - 21 Sep 2015

Cited by 59 | Viewed by 6588

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 [...] Read more.

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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2655 KiB

Open AccessArticle

Nanocrystalline BaSnO₃ as an Alternative Gas Sensor Material: Surface Reactivity and High Sensitivity to SO₂

by Artem Marikutsa, Marina Rumyantseva, Alexander Baranchikov and Alexander Gaskov

Materials 2015, 8(9), 6437-6454; https://doi.org/10.3390/ma8095311 - 18 Sep 2015

Cited by 62 | Viewed by 8412

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 [...] Read more.

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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4950 KiB

Open AccessArticle

A Comparative Study of the Sintering Behavior of Pure and Manganese-Substituted Hydroxyapatite

by Michael Zilm, Seamus D. Thomson and Mei Wei

Materials 2015, 8(9), 6419-6436; https://doi.org/10.3390/ma8095308 - 18 Sep 2015

Cited by 19 | Viewed by 6102

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 [...] Read more.

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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6286 KiB

Open AccessArticle

Development of Chitosan/Bacterial Cellulose Composite Films Containing Nanodiamonds as a Potential Flexible Platform for Wound Dressing

by Fatemeh Ostadhossein, Nafiseh Mahmoudi, Gabriel Morales-Cid, Elnaz Tamjid, Francisco Javier Navas-Martos, Belén Soriano-Cuadrado, José Manuel López Paniza and Abdolreza Simchi

Materials 2015, 8(9), 6401-6418; https://doi.org/10.3390/ma8095309 - 18 Sep 2015

Cited by 93 | Viewed by 9797

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 [...] Read more.

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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1069 KiB

Open AccessArticle

Electroactive Shape Memory Property of a Cu-decorated CNT Dispersed PLA/ESO Nanocomposite

by Javed Alam, Aslam Khan, Manawwer Alam and Raja Mohan

Materials 2015, 8(9), 6391-6400; https://doi.org/10.3390/ma8095313 - 18 Sep 2015

Cited by 28 | Viewed by 7651

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 [...] Read more.

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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707 KiB

Open AccessArticle

Plasma Enhanced Complete Oxidation of Ultrathin Epitaxial Praseodymia Films on Si(111)

by Olga Kuschel, Florian Dieck, Henrik Wilkens, Sebastian Gevers, Jari Rodewald, Christian Otte, Marvin Hartwig Zoellner, Gang Niu, Thomas Schroeder and Joachim Wollschläger

Materials 2015, 8(9), 6379-6390; https://doi.org/10.3390/ma8095312 - 18 Sep 2015

Cited by 5 | Viewed by 7148

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 [...] Read more.

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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2283 KiB

Open AccessArticle

Degradation of Tetracycline with BiFeO₃ Prepared by a Simple Hydrothermal Method

by Zhehua Xue, Ting Wang, Bingdi Chen, Tyler Malkoske, Shuili Yu and Yulin Tang

Materials 2015, 8(9), 6360-6378; https://doi.org/10.3390/ma8095310 - 18 Sep 2015

Cited by 66 | Viewed by 7927

Abstract

BiFeO₃ particles (BFO) were prepared by a simple hydrothermal method and characterized. BFO was pure, with a wide particle size distribution, and was visible light responsive. Tetracycline was chosen as the model pollutant in this study. The pH value was an important [...] Read more.

BiFeO₃ particles (BFO) were prepared by a simple hydrothermal method and characterized. BFO was pure, with a wide particle size distribution, and was visible light responsive. Tetracycline was chosen as the model pollutant in this study. The pH value was an important factor influencing the degradation efficiency. The total organic carbon (TOC) measurement was emphasized as a potential standard to evaluate the visible light photocatalytic degradation efficiency. The photo-Fenton process showed much better degradation efficiency and a wider pH adaptive range than photocatalysis or the Fenton process solely. The optimal residual TOC concentrations of the photocatalysis, Fenton and photo-Fenton processes were 81%, 65% and 21%, while the rate constants of the three processes under the same condition where the best residual TOC was acquired were 9.7 × 10⁻³, 3.2 × 10⁻² and 1.5 × 10⁻¹ min⁻¹, respectively. BFO was demonstrated to have excellent stability and reusability. A comparison among different reported advanced oxidation processes removing tetracycline (TC) was also made. Our findings showed that the photo-Fenton process had good potential for antibiotic-containing waste water treatment. It provides a new method to deal with antibiotic pollution. Full article

(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)

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2671 KiB

Open AccessReview

Heteroepitaxy of Cerium Oxide Thin Films on Cu(111)

by Josef Mysliveček, Vladimir Matolín and Iva Matolínová

Materials 2015, 8(9), 6346-6359; https://doi.org/10.3390/ma8095307 - 18 Sep 2015

Cited by 11 | Viewed by 7480

Abstract

An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced [...] Read more.

An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties. The present contribution is devoted to development of a model catalyst system of CeO₂ (ceria) on the Cu(111) substrate. We propose ways to experimentally characterize and control important parameters of the model catalyst—the coverage of the ceria layer, the influence of the Cu substrate, and the density of surface defects on ceria, particularly the density of step edges and the density and the ordering of the oxygen vacancies. The large spectrum of controlled parameters makes ceria on Cu(111) an interesting alternative to a more common model system ceria on Ru(0001) that has served numerous catalysis studies, mainly as a support for metal clusters. Full article

(This article belongs to the Special Issue Epitaxial Materials 2015)

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1004 KiB

Open AccessArticle

Delineation of First-Order Elastic Property Closures for Hexagonal Metals Using Fast Fourier Transforms

by Nicholas W. Landry and Marko Knezevic

Materials 2015, 8(9), 6326-6345; https://doi.org/10.3390/ma8095303 - 17 Sep 2015

Cited by 31 | Viewed by 4852

Abstract

Property closures are envelopes representing the complete set of theoretically feasible macroscopic property combinations for a given material system. In this paper, we present a computational procedure based on fast Fourier transforms (FFTs) to delineation of elastic property closures for hexagonal close packed [...] Read more.

Property closures are envelopes representing the complete set of theoretically feasible macroscopic property combinations for a given material system. In this paper, we present a computational procedure based on fast Fourier transforms (FFTs) to delineation of elastic property closures for hexagonal close packed (HCP) metals. The procedure consists of building a database of non-zero Fourier transforms for each component of the elastic stiffness tensor, calculating the Fourier transforms of orientation distribution functions (ODFs), and calculating the ODF-to-elastic property bounds in the Fourier space. In earlier studies, HCP closures were computed using the generalized spherical harmonics (GSH) representation and an assumption of orthotropic sample symmetry; here, the FFT approach allowed us to successfully calculate the closures for a range of HCP metals without invoking any sample symmetry assumption. The methodology presented here facilitates for the first time computation of property closures involving normal-shear coupling stiffness coefficients. We found that the representation of these property linkages using FFTs need more terms compared to GSH representations. However, the use of FFT representations reduces the computational time involved in producing the property closures due to the use of fast FFT algorithms. Moreover, FFT algorithms are readily available as opposed to GSH codes. Full article

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2041 KiB

Open AccessArticle

Aspherical Lens Design Using Genetic Algorithm for Reducing Aberrations in Multifocal Artificial Intraocular Lens

by Chih-Ta Yen and Shih-Cyuan Jin

Materials 2015, 8(9), 6309-6325; https://doi.org/10.3390/ma8095305 - 17 Sep 2015

Cited by 6 | Viewed by 6725

Abstract

A complex intraocular lens (IOL) design involving numerous uncertain variables is proposed. We integrated a genetic algorithm (GA) with the commercial optical design software of (CODE V) to design a multifocal IOL for the human eye. We mainly used an aspherical lens in [...] Read more.

A complex intraocular lens (IOL) design involving numerous uncertain variables is proposed. We integrated a genetic algorithm (GA) with the commercial optical design software of (CODE V) to design a multifocal IOL for the human eye. We mainly used an aspherical lens in the initial state to the crystalline type; therefore, we used the internal human eye model in the software. The proposed optimized algorithm employs a GA method for optimally simulating the focusing function of the human eye; in this method, the thickness and curvature of the anterior lens and the posterior part of the IOL were varied. A comparison of the proposed GA-designed IOLs and those designed using a CODE V built-in optimal algorithm for 550 degrees myopia and 175 degrees astigmatism conditions of the human eye for pupil size 6 mm showed that the proposed IOL design improved the spot size of root mean square (RMS), tangential coma (TCO) and modulation transfer function (MTF) at a spatial frequency of 30 with a pupil size of 6 mm by approximately 17%, 43% and 35%, respectively. However, the worst performance of spherical aberration (SA) was lower than 46%, because the optical design involves a tradeoff between all aberrations. Compared with the traditional CODE V built-in optimal scheme, the proposed IOL design can efficiently improve the critical parameters, namely TCO, RMS, and MTF. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2015)

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8644 KiB

Open AccessReview

Fabrication of Nanochannels

by Yuqi Zhang, Xiang-Yu Kong, Loujun Gao, Ye Tian, Liping Wen and Lei Jiang

Materials 2015, 8(9), 6277-6308; https://doi.org/10.3390/ma8095304 - 17 Sep 2015

Cited by 30 | Viewed by 9969

Abstract

Nature has inspired the fabrication of intelligent devices to meet the needs of the advanced community and better understand the imitation of biology. As a biomimetic nanodevice, nanochannels/nanopores aroused increasing interest because of their potential applications in nanofluidic fields. In this review, we [...] Read more.

Nature has inspired the fabrication of intelligent devices to meet the needs of the advanced community and better understand the imitation of biology. As a biomimetic nanodevice, nanochannels/nanopores aroused increasing interest because of their potential applications in nanofluidic fields. In this review, we have summarized some recent results mainly focused on the design and fabrication of one-dimensional nanochannels, which can be made of many materials, including polymers, inorganics, biotic materials, and composite materials. These nanochannels have some properties similar to biological channels, such as selectivity, voltage-dependent current fluctuations, ionic rectification current and ionic gating, etc. Therefore, they show great potential for the fields of biosensing, filtration, and energy conversions. These advances can not only help people to understand the living processes in nature, but also inspire scientists to develop novel nanodevices with better performance for mankind. Full article

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7022 KiB

Open AccessArticle

Material Performance and Animal Clinical Studies on Performance-Optimized Hwangtoh Mixed Mortar and Concrete to Evaluate Their Mechanical Properties and Health Benefits

by Bon-Min Koo, Jang-Ho Jay Kim, Tae-Kyun Kim and Byung-Yun Kim

Materials 2015, 8(9), 6257-6276; https://doi.org/10.3390/ma8095306 - 17 Sep 2015

Cited by 5 | Viewed by 5115

Abstract

In this study, the amount of cement used in a concrete mix is minimized to reduce the toxic effects on users by adjusting the concrete mixture contents. The reduction of cement is achieved by using various admixtures (ground granulated blast-furnace slag, flyash, ordinary [...] Read more.

In this study, the amount of cement used in a concrete mix is minimized to reduce the toxic effects on users by adjusting the concrete mixture contents. The reduction of cement is achieved by using various admixtures (ground granulated blast-furnace slag, flyash, ordinary Portland cement, and activated Hwangtoh powder). To apply the mix to construction, material property tests such as compressive strength, slump, and pH are performed. Preliminary experimental results showed that the Hwangtoh concrete could be used as a healthy construction material. Also, the health issues and effects of Hwangtoh mortar are quantitatively evaluated through an animal clinical test. Mice are placed in Hwangtoh mortar and cement mortar cages to record their activity. For the test, five cages are made with Hwangtoh and ordinary Portland cement mortar floors, using Hwangtoh powder replacement ratios of 20%, 40%, 60%, and 80% of the normal cement mortar mixing ratio, and two cages are made with Hwangtoh mortar living quarters. The activity parameter measurements included weight, food intake, water intake, residential space selection, breeding activity, and aggression. The study results can be used to evaluate the benefits of using Hwangtoh as a cement replacing admixture for lifestyle, health and sustainability. Full article

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4955 KiB

Open AccessArticle

Methanol Adsorption and Reaction on Samaria Thin Films on Pt(111)

by Jin-Hao Jhang, Andreas Schaefer, Volkmar Zielasek, Jason F. Weaver and Marcus Bäumer

Materials 2015, 8(9), 6228-6256; https://doi.org/10.3390/ma8095302 - 17 Sep 2015

Cited by 5 | Viewed by 6269

Abstract

We investigated the adsorption and reaction of methanol on continuous and discontinuous films of samarium oxide (SmO_x) grown on Pt(111) in ultrahigh vacuum. The methanol decomposition was studied by temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS), while structural [...] Read more.

We investigated the adsorption and reaction of methanol on continuous and discontinuous films of samarium oxide (SmO_x) grown on Pt(111) in ultrahigh vacuum. The methanol decomposition was studied by temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS), while structural changes of the oxide surface were monitored by low-energy electron diffraction (LEED). Methanol dehydrogenates to adsorbed methoxy species on both the continuous and discontinuous SmO_x films, eventually leading to the desorption of CO and H₂ which desorbs at temperatures in the range 400–600 K. Small quantities of CO₂ are also detected mainly on as-prepared Sm₂O₃ thin films, but the production of CO₂ is limited during repeated TPD runs. The discontinuous film exhibits the highest reactivity compared to the continuous film and the Pt(111) substrate. The reactivity of methanol on reduced and reoxidized films was also investigated, revealing how SmO_x structures influence the chemical behavior. Over repeated TPD experiments, a SmO_x structural/chemical equilibrium condition is found which can be approached either from oxidized or reduced films. We also observed hydrogen absence in TPD which indicates that hydrogen is stored either in SmO_x films or as OH groups on the SmO_x surfaces. Full article

(This article belongs to the Special Issue Epitaxial Materials 2015)

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Graphical abstract

2423 KiB

Open AccessArticle

Tube-Super Dielectric Materials: Electrostatic Capacitors with Energy Density Greater than 200 J·cm⁻³

by Francisco Javier Quintero Cortes and Jonathan Phillips

Materials 2015, 8(9), 6208-6227; https://doi.org/10.3390/ma8095301 - 17 Sep 2015

Cited by 14 | Viewed by 6981

Abstract

The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm⁻³, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, [...] Read more.

The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm⁻³, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are reported. The first generation super dielectric materials (SDM) are multi-material mixtures with dielectric constants greater than 1.0 × 10⁵, composed of a porous, electrically insulating powder filled with a polarizable, ion-containing liquid. Second-generation SDMs (TSDM), introduced here, are anodic titania nanotube arrays filled with concentrated aqueous salt solutions. Capacitors using TiO₂ based TSDM were found to have dielectric constants at ~0 Hz greater than 10⁷ in all cases, a maximum operating voltage of greater than 2 volts and remarkable energy density that surpasses the highest previously reported for EC capacitors by approximately one order of magnitude. A simple model based on the classic ponderable media model was shown to be largely consistent with data from nine EC type capacitors employing TSDM. Full article

(This article belongs to the Section Energy Materials)

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2900 KiB

Open AccessArticle

Influence of Ultrafine 2CaO·SiO₂ Powder on Hydration Properties of Reactive Powder Concrete

by Hongfang Sun, Zishanshan Li, Shazim Ali Memon, Qiwu Zhang, Yaocheng Wang, Bing Liu, Weiting Xu and Feng Xing

Materials 2015, 8(9), 6195-6207; https://doi.org/10.3390/ma8095300 - 17 Sep 2015

Cited by 20 | Viewed by 7122

Abstract

In this research, we assessed the influence of an ultrafine 2CaO·SiO₂ powder on the hydration properties of a reactive powder concrete system. The ultrafine powder was manufactured through chemical combustion method. The morphology of ultrafine powder and the development of hydration products [...] Read more.

In this research, we assessed the influence of an ultrafine 2CaO·SiO₂ powder on the hydration properties of a reactive powder concrete system. The ultrafine powder was manufactured through chemical combustion method. The morphology of ultrafine powder and the development of hydration products in the cement paste prepared with ultrafine powder were investigated by scanning electron microscopy (SEM), mineralogical composition were determined by X-ray diffraction, while the heat release characteristics up to the age of 3 days were investigated by calorimetry. Moreover, the properties of cementitious system in fresh and hardened state (setting time, drying shrinkage, and compressive strength) with 5% ordinary Portland cement replaced by ultrafine powder were evaluated. From SEM micrographs, the particle size of ultrafine powder was found to be up to several hundred nanometers. The hydration product started formulating at the age of 3 days due to slow reacting nature of belitic 2CaO·SiO₂. The initial and final setting times were prolonged and no significant difference in drying shrinkage was observed when 5% ordinary Portland cement was replaced by ultrafine powder. Moreover, in comparison to control reactive powder concrete, the reactive powder concrete containing ultrafine powder showed improvement in compressive strength at and above 7 days of testing. Based on above, it can be concluded that the manufactured ultrafine 2CaO·SiO₂ powder has the potential to improve the performance of a reactive powder cementitious system. Full article

(This article belongs to the Section Advanced Composites)

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7478 KiB

Open AccessArticle

Effect of Heat Treatment Process on Microstructure and Fatigue Behavior of a Nickel-Base Superalloy

by Peng Zhang, Qiang Zhu, Gang Chen, Heyong Qin and Chuanjie Wang

Materials 2015, 8(9), 6179-6194; https://doi.org/10.3390/ma8095299 - 16 Sep 2015

Cited by 16 | Viewed by 8183

Abstract

The study of fatigue behaviors for nickel-base superalloys is very significant because fatigue damage results in serious consequences. In this paper, two kinds of heat treatment procedures (Pro.I and Pro.II) were taken to investigate the effect of heat treatment on microstructures and fatigue [...] Read more.

The study of fatigue behaviors for nickel-base superalloys is very significant because fatigue damage results in serious consequences. In this paper, two kinds of heat treatment procedures (Pro.I and Pro.II) were taken to investigate the effect of heat treatment on microstructures and fatigue behaviors of a nickel-base superalloy. Fatigue behaviors were studied through total strain controlled mode at 650 °C. Manson-Coffin relationship and three-parameter power function were used to predict fatigue life. A good link between the cyclic/fatigue behavior and microscopic studies was established. The cyclic deformation mechanism and fatigue mechanism were discussed. The results show that the fatigue resistance significantly drops with the increase of total strain amplitudes. Manson-Coffin relationship can well predict the fatigue life for total strain amplitude from 0.5% to 0.8%. The fatigue resistance is related with heat treatment procedures. The fatigue resistance performance of Pro.I is better than that of Pro.II. The cyclic stress response behaviors are closely related to the changes of the strain amplitudes. The peak stress of the alloy gradually increases with the increase of total strain amplitudes. The main fracture mechanism is inhomogeneous deformation and the different interactions between dislocations and γ′ precipitates. Full article

(This article belongs to the Special Issue Failure Analysis in Materials)

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5741 KiB

Open AccessArticle

First-Principles Investigation of Adsorption and Diffusion of Ions on Pristine, Defective and B-doped Graphene

by Wei Wan and Haidong Wang

Materials 2015, 8(9), 6163-6178; https://doi.org/10.3390/ma8095297 - 15 Sep 2015

Cited by 40 | Viewed by 7536

Abstract

We performed first-principles calculations to reveal the possibility of applying pristine, defective, and B-doped graphene in feasible negative electrode materials of ion batteries. It is found that the barriers for ions are too high to diffuse through the original graphene, however the reduced [...] Read more.

We performed first-principles calculations to reveal the possibility of applying pristine, defective, and B-doped graphene in feasible negative electrode materials of ion batteries. It is found that the barriers for ions are too high to diffuse through the original graphene, however the reduced barriers are obtained by introducing defects (single vacancy, double vacancy, Stone–Wales defect) in the graphene. Among the three types of defects, the systems with a double vacancy could provide the lowest barriers of 1.49 and 6.08 eV for Li and Na, respectively. Furthermore, for all kinds of B-doped graphene with the vacancy, the systems with a double vacancy could also provide the lowest adsorption energies and diffusion barriers. Therefore, undoped and B-doped graphene with a double vacancy turn out to be the most promising candidates that can replace pristine graphene for anode materials in ion batteries. Full article

(This article belongs to the Special Issue Graphene)

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3971 KiB

Open AccessArticle

Three-Point Bending Fracture Behavior of Single Oriented Crossed-Lamellar Structure in Scapharca broughtonii Shell

by Hong-Mei Ji, Wen-Qian Zhang, Xu Wang and Xiao-Wu Li

Materials 2015, 8(9), 6154-6162; https://doi.org/10.3390/ma8095298 - 15 Sep 2015

Cited by 14 | Viewed by 6019

Abstract

The three-point bending strength and fracture behavior of single oriented crossed-lamellar structure in Scapharca broughtonii shell were investigated. The samples for bending tests were prepared with two different orientations perpendicular and parallel to the radial ribs of the shell, which corresponds to the [...] Read more.

The three-point bending strength and fracture behavior of single oriented crossed-lamellar structure in Scapharca broughtonii shell were investigated. The samples for bending tests were prepared with two different orientations perpendicular and parallel to the radial ribs of the shell, which corresponds to the tiled and stacked directions of the first-order lamellae, respectively. The bending strength in the tiled direction is approximately 60% higher than that in the stacked direction, primarily because the regularly staggered arrangement of the second-order lamellae in the tiled direction can effectively hinder the crack propagation, whereas the cracks can easily propagate along the interfaces between lamellae in the stacked direction. Full article

(This article belongs to the Section Biomaterials)

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8845 KiB

Open AccessArticle

Pyrolysis Model Development for a Multilayer Floor Covering

by Mark B. McKinnon and Stanislav I. Stoliarov

Materials 2015, 8(9), 6117-6153; https://doi.org/10.3390/ma8095295 - 14 Sep 2015

Cited by 35 | Viewed by 7630 | Correction

Abstract

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design [...] Read more.

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m⁻², which is within the mean experimental uncertainty. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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1162 KiB

Open AccessArticle

The Photoluminescent Properties of New Cationic Iridium(III) Complexes Using Different Anions and Their Applications in White Light-Emitting Diodes

by Hui Yang, Guoyun Meng, Yayun Zhou, Huaijun Tang, Jishou Zhao and Zhengliang Wang

Materials 2015, 8(9), 6105-6116; https://doi.org/10.3390/ma8095296 - 14 Sep 2015

Cited by 17 | Viewed by 7050

Abstract

Three cationic iridium(III) complexes [Ir(ppy)₂(phen)][PF₆] (C1), [Ir(ppy)₂(phen)]₂SiF₆ (C2) and [Ir(ppy)₂(phen)]₂TiF₆ (C3) (ppy: 2-phenylpyridine, phen: 1, 10-phenanthroline) using different anions were synthesized and characterized by ¹H Nuclear magnetic resonance [...] Read more.

Three cationic iridium(III) complexes [Ir(ppy)₂(phen)][PF₆] (C1), [Ir(ppy)₂(phen)]₂SiF₆ (C2) and [Ir(ppy)₂(phen)]₂TiF₆ (C3) (ppy: 2-phenylpyridine, phen: 1, 10-phenanthroline) using different anions were synthesized and characterized by ¹H Nuclear magnetic resonance (¹HNMR), mass spectra (MS), Fourier transform infrared (FTIR) spectra and element analysis (EA). After the ultraviolet visible (UV-vis) absorption spectra, photoluminescent (PL) properties and thermal properties of the complexes were investigated, complex C1 and C3 with good optical properties and high thermal stability were used in white light-emitting diodes (WLEDs) as luminescence conversion materials by incorporation with 460 nm-emitting blue GaN chips. The integrative performances of the WLEDs fabricated with complex C1 and C3 are better than those fabricated with the widely used yellow phosphor Y₃Al₅O₁₂:Ce³⁺ (YAG). The color rendering indexes of the WLEDs with C1 and C3 are 82.0 and 82.6, the color temperatures of them are 5912 K and 3717 K, and the maximum power efficiencies of them are 10.61 Lm·W⁻¹ and 11.41 Lm·W⁻¹, respectively. Full article

(This article belongs to the Special Issue Developments in Organic Dyes and Pigments)

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902 KiB

Open AccessArticle

Behaviour of Passive Fire Protection K-Geopolymer under Successive Severe Fire Incidents

by Konstantinos Sakkas, Alexandros Sofianos, Pavlos Nomikos and Dimitrios Panias

Materials 2015, 8(9), 6096-6104; https://doi.org/10.3390/ma8095294 - 11 Sep 2015

Cited by 40 | Viewed by 5422

Abstract

The performance of a fire resistant coating for tunnel passive fire protection under successive severe thermal loading is presented. The material falls under the class of potassium based geopolymers (K-geopolymer) and was prepared by mixing ferronickel (FeNi) slag, doped with pure alumina, with [...] Read more.

The performance of a fire resistant coating for tunnel passive fire protection under successive severe thermal loading is presented. The material falls under the class of potassium based geopolymers (K-geopolymer) and was prepared by mixing ferronickel (FeNi) slag, doped with pure alumina, with a highly alkaline potassium hydroxide aqueous phase. Its performance was assessed by subjecting a concrete slab with a five cm thick K-geopolymer coating layer into successive RijksWaterStaat (RWS) fire incidents. During the first test, the maximum measured temperature in the K-geopolymer/concrete interface was 250 °C, which is 130 °C lower than the RWS test requirement, while, during the second fire test, the maximum temperature was almost 370 °C, which is still lower than the RWS requirement proving the effectiveness of the material as a thermal barrier. In addition, the material retained its structural integrity, during and after the two tests, without showing any mechanical or thermal damages. Full article

(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)

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