Editorial
Hisatoshi Kobayashi; Mikael Syväjärvi
Review Article
Berenika Hausnerova
Abstract
Regardless of high demands on properties of powder injection molding (PIM) compounds, there is still uncertainty in the role of the polymer binder in the process. To a great extent this is caused by the relatively low number of suitable direct methods to observe the interactions among binder components ...
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Regardless of high demands on properties of powder injection molding (PIM) compounds, there is still uncertainty in the role of the polymer binder in the process. To a great extent this is caused by the relatively low number of suitable direct methods to observe the interactions among binder components as well as binder-powder and binder-powder-processing tool reactions, because of the complexity of occurring interactions. In this paper the review of state-of-art in the field of binder development and characterization is reported with the special regard to methods to quantify their mutual relationship. Copyright © 2017 VBRI Press
Martin Wilhelm; Mikael Syväjärvi; Peter J. Wellmann
Abstract
Among the various SiC polytypes, cubic 3C‐SiC is much more difficult to grow in high crystalline quality than the commercially introduced hexagonal 6H‐SiC and 4H‐SiC counterparts. Besides some benefits of 3C‐SiC for transistor applications related to a greater electron mobility and a lower metal‐oxide‐semiconductor ...
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Among the various SiC polytypes, cubic 3C‐SiC is much more difficult to grow in high crystalline quality than the commercially introduced hexagonal 6H‐SiC and 4H‐SiC counterparts. Besides some benefits of 3C‐SiC for transistor applications related to a greater electron mobility and a lower metal‐oxide‐semiconductor interface trap density compared to 4H‐SiC, new potential optoelectronic applications have been introduced very recently. Boron doped 3C‐SiC may act as an ideal candidate for an intermediate band (IB) solar cell material. Aluminum doped p‐type 3C‐SiC could lead to the development of efficient optoelectrochemical water splitting cells. Finally, 3C‐SiC with its various intrinsic point defects has been considered as a suitable candidate for future spintronic‐applications. All these applications will critically depend on further understanding defect behaviour on atomic level. In our study we investigated free standing n‐type and p‐type 3C‐SiC material grown in our lab. Temperature dependent photoluminescence measurements revealed the presence of carbon vacancy related VC and VC-CSi defect transitions in the p‐type materials but not in the n‐type materials. This observation present in as grown 3C-SiC is believed to have significant impact on the optoelectronic applications. Copyright © 2017 VBRI Press.
Research Article
Michael Schoeler; Philipp Schuh; Grazia Litrico; Francesco La Via; Marco Mauceri .; Peter J. Wellmann
Abstract
In this article, sublimation growth of 3C-SiC on 3C-SiC-on-Si seeding layers was evaluated by characterizing the densities of protrusions and stacking faults (SF). Both defects are among the most critical concerning the growth process and the realization of high quality material for device applications. ...
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In this article, sublimation growth of 3C-SiC on 3C-SiC-on-Si seeding layers was evaluated by characterizing the densities of protrusions and stacking faults (SF). Both defects are among the most critical concerning the growth process and the realization of high quality material for device applications. By variation of growth parameters like temperature, growth rate and 3C-SiC-thickness we conducted a series of experiments and characterized these layers by optical microscopy and KOH etching. The protrusion density is predetermined by the seeding layers and was kept at a constant level, whereas a decrease of SF-density was observed with increasing layer thickness during subsequent sublimation growth steps. Therefore, in the case of Sublimation Epitaxy (SE) it has been found appropriate to distinguish between defects that can be reduced during SE and defects that are merely reproduced from the seeding material during sublimation growth. Furthermore, a weak trend towards a decrease of SF-density with increasing growth temperature was observed. The findings in this work demonstrates the potential of SE in growing thick and high-quality 3C-SiC layers if sufficiently good seeding layers were available. Copyright © 2017 VBRI Press.
Research Article
Dessislava DImova; Stoyan Pisov; Proykova .
Abstract
At the nanoscale defects (vacancies) can be useful for generating novel materials and devices. In this paper we discuss how a bi-vacancy orientation in bilayer graphene influences the total magnetization of the system. The spin-polarized density functional theory as implemented in the Quantum Espresso ...
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At the nanoscale defects (vacancies) can be useful for generating novel materials and devices. In this paper we discuss how a bi-vacancy orientation in bilayer graphene influences the total magnetization of the system. The spin-polarized density functional theory as implemented in the Quantum Espresso code is used to calculate the total magnetization for the case of graphene sheets with the same or different vacancy distributions. Important results are obtained: reduction of the magnetic moment due to the interlayer bonding in AA bilayer stack with a double vacancy in each graphene layer on the top of each other; out-off plane arrangement of the carbon atoms in the vicinity of the vacanices; opening of a gap in the band structure due to vacancies. It could be expected that the temperature and the interface will further influence the life-time of the magnetic state but the possibility of switching between non-magnetic, antiferromagnetic and ferromagnetic states as a result of mutual rotation of the defective layers remains. Copyright © 2017 VBRI Press
Research Article
Hao Xin; Huigao Chen; Jiarong Lu; Junkun Tang; Qiaolong Yuan; Farong Huang
Abstract
A Si-containing arylether arylacetylene resin, poly(dimethylsilyene-ethynylene-phenyleneetherene-ethynylene) (PSEE), was synthesized from diethynyldiphenyl ether and dichlorosilane through Grignard reactions. The structures and properties of PSEE resin were characterized by NMR, FT-IR, DSC, TGA analysis ...
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A Si-containing arylether arylacetylene resin, poly(dimethylsilyene-ethynylene-phenyleneetherene-ethynylene) (PSEE), was synthesized from diethynyldiphenyl ether and dichlorosilane through Grignard reactions. The structures and properties of PSEE resin were characterized by NMR, FT-IR, DSC, TGA analysis techniques. PSEE resin can be crosslinked to form a thermoset at a temperature less than 2000C. There is no glass transition in the temperature range of RT~5000C and Td5 is 5680C in N2 for PSEE thermoset. The thermoset shows good dielectric properties and its glass fiber reinforced composite exhibits high mechanical properties. Copyright © 2017 VBRI Press.
Research Article
Zdeněk Prošek; Jan Trejbal; Pavel Tesárek; Lubomír Kopecký
Abstract
This work deals with a utilization of a plasma treatment of polymeric macro-fibers used as reinforcement in the cement composites. Commercial fibers BeneSteel were plasma treated to reduce their weaknesses – smooth and chemically inert surfaces and thus to enhance an interfacial shear strength ...
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This work deals with a utilization of a plasma treatment of polymeric macro-fibers used as reinforcement in the cement composites. Commercial fibers BeneSteel were plasma treated to reduce their weaknesses – smooth and chemically inert surfaces and thus to enhance an interfacial shear strength between them and the cement matrix. The low-pressure cold oxygen plasma treatment was done for both physical (roughening) and chemical (surface activation via active polar groups) surface modifications. A plasma exposition time differed between 5 and 480 seconds, while the surface changes were observed. It was shown that the most effective treatment time was equal to 30 seconds, as proven by a wettability measurement between fibers and demineralised water. To determine the interfacial shear strength between reference and chosen modified fibers, pull out tests from the cement matrix was performed. Finally, thus treated fibers were used as the reinforcement in concrete composites. Concrete samples having dimension equal to 100 × 100 × 400 mm were tested in the three-point bending test. We focused especially on the post-cracking response of tested samples. The results showed that the post-cracking residual flexural strength of samples reinforced with plasma treated fibers was higher by 30 %. It was find out that the utilization of plasma treated fibers is more effective if compared to reference ones. Copyright © 2017 VBRI Press.
Research Article
Andris Berzins; Andris Morozovs; Jan Van den Bulcke; Joris Van Acker
Abstract
Research describes softwood – pine (Pinus sylvestris L.) and spruce (Picea abies [L.] Karst) and hardwood – birch(Betula pendula Roth) binding with inorganic geopolymer binder, the main focus is on the softwood and geopolymerbinding principles. Geopolymer binder is formed from calcined clay ...
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Research describes softwood – pine (Pinus sylvestris L.) and spruce (Picea abies [L.] Karst) and hardwood – birch(Betula pendula Roth) binding with inorganic geopolymer binder, the main focus is on the softwood and geopolymerbinding principles. Geopolymer binder is formed from calcined clay and liquid glass. The research describesgeopolymer binder compositions with various ratios of liquid glass and clay. This research focuses on mechanicalstrength of bonded wood samples in shear test and on visualization of binder in three dimensions using X-ray computed tomography with submicron resolution. The scan results are compared with mechanical strength test results. The resultsof the research shows, that inorganic binder with spruce wood can achieve 7 MPa shear strength. The research describes binding principles that function between wood and geopolymer and explains the main reasons for destruction of joint. Copyright © 2017 VBRI Press.
Research Article
Giuseppe Napoli; Sabrina Mengaroni; Marco Rallini; Luigi Torre; Andrea Di Schino
Abstract
The present study is focused on analyzing the effect of the interrupted quenching followed by a partitioning process in a high carbon steel 0.50C-1.50Mn-0.40Si-2.00 Cr without significant contribution of Al. Thermal treatments were performed at laboratory scale in a quenching dilatometer Linseis R.I.T.A ...
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The present study is focused on analyzing the effect of the interrupted quenching followed by a partitioning process in a high carbon steel 0.50C-1.50Mn-0.40Si-2.00 Cr without significant contribution of Al. Thermal treatments were performed at laboratory scale in a quenching dilatometer Linseis R.I.T.A RL78. The fractions of retained austenite were evaluated by scanning electron microscope. The temperature for the interrupted quenching phase was evaluated based on the Koistenen and Marburger equation (adapted to the 0.50C steel) and the result highlights a correlation between the chosen different temperature of quenching and the fraction of retained austenite formed during the quenching step of the process. Copyright © 2017 VBRI Press.
Research Article
Sweta Karmakar Ghosh; Vikram Thakur; Shubhajit Roy Chowdhury
Abstract
Magnetic Resonance Imaging is a non-invasive technique which basically consists of a main magnet, gradients, radio-frequency transmitter and receiver and scanner. Commercially available MR scanners are quite heavy. However this bio-device can be made low cost, low weight and also low magnetic field. ...
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Magnetic Resonance Imaging is a non-invasive technique which basically consists of a main magnet, gradients, radio-frequency transmitter and receiver and scanner. Commercially available MR scanners are quite heavy. However this bio-device can be made low cost, low weight and also low magnetic field. This work proposes the design and development of a low magnetic field MRI scanner of 0.2T magnetic field strength. This design is based on Helmholtz coil as the main magnet. The homogeneity observed within a radius of 15cm was about 2% in a coil of 30cm radius. While at the centre homogeneity was found much better. Strength of 75µT/m gradient magnetic field has been considered for the design. Maxwell coil has been used for longitudinal gradient and Saddle coil has been used for transverse gradient. The resonant frequency was obtained 8.516MHz for a main magnetic field of 0.2T for protons. Simulation results for magnetic flux density norm had been obtained for Helmholtz coil and Maxwell coil depicting the distribution of magnetic flux density. Also weight of the main magnet had been found to be quite less when compared with main magnet that are commercially used. Copyright © 2017 VBRI Press.
Research Article
Ioannis Tsiaoussis; Nikos D. Charisiou; Maria A. Goula; Lazaros Tzounis; George Vourlias; oannis V. Yentekakis; Remi Chassagnon; Valerie Potin; Bruno Domenichini
Abstract
In the present work, we investigated the structural morphology of carbon species deposited on nickel catalysts supported on CeO2-ZrO2 (18.8 wt.% ceria), prepared by wet impregnation, during the dry reforming of methane (DRM) reaction by using Thermo-gravimetric Analysis (TGA), Raman Spectroscopy, ...
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In the present work, we investigated the structural morphology of carbon species deposited on nickel catalysts supported on CeO2-ZrO2 (18.8 wt.% ceria), prepared by wet impregnation, during the dry reforming of methane (DRM) reaction by using Thermo-gravimetric Analysis (TGA), Raman Spectroscopy, X-ray diffraction (XRD), High Resolution TransmissionElectron Microscopy (HRTEM) and Scanning Transmission Electron Microscopy- Energy dispersive spectroscopy(STEM-EDS). TGA results show that the amount of deposited carbon decreases upon increasing reaction temperature, which is consistent with the thermodynamics of the reactions responsible for carbon formation, and Raman analysis points to a simultaneous increase in its graphitization degree. XRD measurements reveal the existence of 2H-Graphite and TEM imaging mode as well as SAED patterns depict that in all temperatures under which the catalysts were tested (550, 650, 750 and 800 oC), the formation of multi wall carbon nanotubes (MWCNT). HRTEM observations also reveal that the Ni nanoparticles are often enclosed by the MWCNT. HRTEM images identify nanocrystalline areas with a tetragonal phase, P42/nmc(137), of Ce1-xZrxO2, and STEM-EDS analysis at the nanometer scale confirms a correlation between Ce and Zr in the average atomic ratio (% ), 1 to 5.19 - 6.94 respectively. The results presented herein confirm that biogas mixtures can be used as precursors for the production of MWCNTs. Copyright © 2017 VBRI Press
Research Article
Hamood Al Kharusi; Mozhgan Svensson; Babak Salamatinia; Bahman Amini Horri
Abstract
NiO/YSZ (nickel oxide / yttria-stabilized zirconia) is the state-of-the-art anode composite for fabrication of high-temperature solid oxide fuel cells (SOFCs). In this study, nanocomposite powder of NiO/YSZ was synthesized by thermal treatment of the gel beads formed by extrusion dripping of sodium alginate ...
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NiO/YSZ (nickel oxide / yttria-stabilized zirconia) is the state-of-the-art anode composite for fabrication of high-temperature solid oxide fuel cells (SOFCs). In this study, nanocomposite powder of NiO/YSZ was synthesized by thermal treatment of the gel beads formed by extrusion dripping of sodium alginate solution into an aqueous solution of Ni+2, Y+3, and Zr+4. The NiO/YSZ nanocomposite powder was prepared by calcination (thermal decomposition) of the dried beads in a muffle furnace at 400°C-600°C for 6 hours. The as prepared powders were characterised by TGA, XRD, FESEM, and TEM techniques. The TGA results of the dried beads showed that the thermal degradation begins at 135°C which is followed by a total mass loss of around 75.0% at 600°C. The morphology analysis of the sample (by FESEM and TEM images) showed a relatively uniform particle size distribution of the powder with an average particle size of 5-25 nm that was confirmed by the XRD crystal size calculations. The electrochemical performance measurement of the fabricated cell using the synthesized NiO/YSZ showed a maximum power density of 1143 mW/cm2 at 850°C under hydrogen stream at 20 ml/min. Copyright © 2017 VBRI Press.
Research Article
Sunita Barot; Neelkumar Gadhiya; Maaz Nawab; Rajib. Bandyopadhyay
Abstract
Sulphated zirconia, one of the most efficient solid acid catalysts, has been explored in present studies for transesterification reaction. The catalyst was synthesized by conventional precipitation method and characterized by XRD, TGA, FTIR and total acidity. The catalyst exhibits excellent activity ...
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Sulphated zirconia, one of the most efficient solid acid catalysts, has been explored in present studies for transesterification reaction. The catalyst was synthesized by conventional precipitation method and characterized by XRD, TGA, FTIR and total acidity. The catalyst exhibits excellent activity for transesterification of model triglyceride triacetin as well as Jatropha oil with high selectivity towards the formation of monoalkyl esters. Influence of various reaction parameters such as triglyceride/alcohol molar ratio, catalyst amount, reaction temperature and reaction time on catalytic performance were studied over model triglyceride. The maximum 96 % yield of methyl acetate was achieved in 3 hours at 10 wt% catalyst loading with triglyceride to methanol ratio 1:15 and 70o C reaction temperature. The kinetic studies were also done and found that reaction follows first order kinetics and reaction rates are not mass transfer limited. The optimized reaction parameters were extended for biodiesel synthesis from Jatropha oil and FAME yield of 82 % could be successfully achieved. Hence, Sulphated zirconia is a promising catalyst for heterogeneous transesterification of triglycerides, which is more productive and environment-friendly as compared to conventional homogeneous transesterification. Copyright © 2017 VBRI Press.