bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Interfacial Charge Transfer Loss in Hybrid Solar Cells by Impedance Spectroscopy
Authors: Hidayat Rahmat , Handayani Yolla Sukma , Wulandari Priastuti
Published: August 2015

Organic solar cells have been much studied because of the simplicity in their fabrication process in comparison to solar cells based on crystalline inorganic semiconductors. However, the actual power conversion efficiency is still much lower than the theoretical prediction, which may indicate the effect of inefficient charge transfer or charge recombination loss inside the cell. We have studied the photovoltaic characteristics of hybrid solar cells with transition metal doped ZnO layer as electron transport layers. Under dark condition, their J-V curves show a deviation from an ideal diode characteristic, which is indicated by current flow below the threshold voltage. Further investigations to clarify the photovoltaic characteristics of those cells were then carried out by the measurements of impedance spectroscopy. The impedance characteristics are dependent on the transport layer used, where the Nyquist plots of cells with TiZO exhibit larger impedance than those of cells with ZnO. However, those cells with larger impedance show better working performances. This fact was then interpreted as the result from smaller interfacial charge transfer loss, which may take place via charge carrier recombination at the interface of the transport layer and active layer, in the cells with TiZO.
Optical Property Enhancement of Silica-Modified Polyaniline Grown on Glass Substrate via Incorporation of Zinc Sulfide into the Polymer Matrix
Authors: Potestas Melchor Jocanain , Alguno Arnold C. , Vequizo Reynaldo M. , Sambo Bianca Rae B. , Odarve Majvell Kay G.
Published: August 2015

Growth of zinc sulfide (ZnS) nanostructures on silica modified-polyaniline (SM-PAni) with polymerization time-dependent was prepared using chemical bath deposition (CBD) technique. The grown samples were characterized by scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. SEM images revealed some voids in the nanocomposites. The average diameter of the grown ZnS nanospheres did not significantly change by changing the growth time of the polyaniline. FTIR spectra and UV-Vis absorption spectra revealed the partial transformation of emeraldine salt polyaniline into emeraldine base PAni due to the deprotonation triggered during CBD for the synthesis of ZnS nanostructures. Furthermore, UV-Vis absorption spectra reveal synergistic effect of the absorption bands of both polyaniline and ZnS nanostructures. This synergistic effect results to the enhancement in the optical property of the fabricated nanocomposite which is an essential property in optoelectronics and solar cell application.
Explorative Synthesis of Magnetic Ca-Fe-O Compounds by Mixing Precipitated CaCO3 from Limestone and Iron Sand Extracted – Fe2O3.H2O
Authors: Mastuki  , Baqiya Malik Anjelh , Darminto
Published: August 2015

Synthesis of Ca-Fe-O using solution mixing method employing CaCO3 and Fe2O3•H2O has been conducted. Extraction of limestone as the raw material of precipitated calcium carbonate (PCC) and iron sands as that of Fe2O3•H2O was prepared to explore various compound of C-Fe-O, where the CaFe4O7 phase is mainly expected. The PCC and Fe2O3•H2O each are dissolved in 1 M HNO3 and mixed to be most homogeneous. The results of the synthesis are characterized by DTA/GTA and then sintered at temperatures of 800°C, 900°C and 1000°C.The sintered samples were characterized by XRD, FTIR, and VSM. The sintering temperature at 800°C, 900°C and 1000°C gave result the phase content of CaFe4O7 being respectively 55.42%, 44.55% and 36.39%. Other major phases in the Ca-Fe-O samples consist of Ca2Fe9O13 and Ca4Fe14O25. The remanence value of the corresponding samples is 2.11, 1.28, and 1.74 emu/g respectively.
Electronic Structure of Muonated La2CuO4
Authors: Rozlan Ainul Fauzeeha , Sulaiman Shukri , Mohamed-Ibrahim M.I. , Watanabe Isao
Published: August 2015

We have performed First Principle computational studies utilizing Molecular-Orbital (MO) Cluster method to examine the electronic structure of muonated La2CuO4. Based on recent works, we investigated three suggested muon sites in La2CuO4. Two possible muon sites are located near the apical oxygen O(a), and the other one is near the planar oxygen O(p). The calculations were performed at the HF/Gen level of theory. The results of our investigation show that there is a very significant covalency effect between copper and oxygen. In the pure system, the effective charge on Cu is 0.77 while the charge on the oxygens is around –1.8. In the muonated system, the charge on Cu reduces to 0.58. The spin density at Cu is 0.78 in the pure system and becomes 0.70 when muon is added. As for the muon, the charge and spin density are +0.22 and –0.0026 respectively.
Study of Thermal Conductivity due to Spins in One-Dimensional Spin Systems AFeX3 (A=Rb, Cs; X=Cl, Br)
Authors: Tasomara Riesma , Kawamata T. , Matsuoka Y. , Sudo H. , Naruse K. , Ohno M. , Nagasawa H. , Hagiya Y. , Sasaki T. , Risdiana  , Koike Yoji
Published: August 2015

Large contributions of the thermal conductivity due to spins, κspin, in low-dimensional spin systems are expected to be utilized as highly thermal conducting materials. One-dimensional spin system RbFeCl3 with ferromagnetic chains and CsFeBr3 with antiferromagnetic chains in magnetic fields have been prepared in order to observe the contribution of κspin to the value of thermal conductivity. The temperature dependence of the thermal conductivity parallel to spin chains along the c-axis, κ//c, of RbFeCl3 enhanced around 3 K and 10 K by the application of magnetic field. In the thermal conductivity perpendicular to c-axis, κ⊥c, of RbFeCl3, on the other hand, it has been found that only one peak around 3 K is enhanced by the application of magnetic field. Since κ⊥c is mainly owing to the thermal conductivity due to phonons, κphonon, it has been concluded the peak of κ//c around 10 K in magnetic fields is due to the contribution of κspin. For CsFeBr3, it has been found that κ//c shows two peaks around 3 K and 25 K while κ⊥c shows one peak around 12 K in zero field. This indicates that there is a marked contribution of κspin to κ//c. κ⊥ However, the details of the marked contribution of κspin to κ//c are not yet clear, since κ//c has been suppressed by the application of magnetic field in contrast with the enhancement of the thermal conductivity in RbFeCl3.
Modification of Polystyrene Morphology and its Influence to the Coated Zinc Phthalocyanine Layer and Frequency Change in QCM Sensor
Authors: Masruroh  , Djoko D.J.D.H. , Didik Lalu A. , Rachmawati Eka , Robiandi Fadli , Padaga Masdiana , Sakti S.P.
Published: August 2015

This study observed the influence of solvents on polystyrene regarding the layered morphologies of zinc phthalocyanine (ZnPc) and its influence on the bovine serum albumin (BSA) immobilization on quartz crystal microbalance (QCM) sensor. The larger surface width introduced by surface roughness of the polystyrene due to chloroform (CHCl3) as the solvents allows more ZnPc to be trapped within the polystyrene. Moreover, the wider surface width also increases the amount of ZnPc to be deposited on top of the polystyrene surface. Therefore, the ZnPc layer deposited onto polystyrene created with CHCl3 solvent is thicker than other solvents, which result in the largest ∆f of the ZnPc layer.
Study on Phase, Molecular Bonding, and Bandgap of Reduced Graphene Oxide Prepared by Heating Coconut Shell
Authors: Nugraheni Ananda Yogi , Nasrullah Muhammad , Prasetya Fandi Angga , Astuti Fahmi , Darminto
Published: August 2015

The purpose of this work is to search reduced graphene oxide (RGO) phase by identifying the molecular bonding, energy band gap and phase of old coconut shell. The characterization was performed by using FTIR, Uv-Vis and XRD spectroscopy. The heating temperature used in this work was 400°C and 600°C.Furthermore, the type of heating atmosphere used in this research covers nitrogen, ambient air with and without rinsing step. The XRD analysis shows that the RGO phase is formed by turbostatic structure which is a pile of random arrangement of parallel layers that make up the graphite structure with cliftonite phase at temperature 400°C and 600°C. In the inert nitrogen gas treatment, there are two impurity phases such as potassium chlorate (KClO4) and sulfur (S11). The molecular bondings of C=C, C-C, C-O, C=O, C-H and O-H appeared on the FTIR spectra of the samples were indentified. Analysis by using linear regression and absorbance edge methods was conducted to result in energy gap in the range from 0.14 to 0.67 eV, indicating that the produced samples are semiconducting materials.
Study of Raman Spectroscopy on Graphene Phase from Heat Treatment of Coconut (Cocus nucifera) Shell
Authors: Prasetya Fandi Angga , Nasrullah Muhammad , Nugraheni Ananda Yogi , Darminto
Published: August 2015

Coconut (Cocus Nucifera) shell as the main ingredient in this research has been heat-treated at temperature of 1000°C in atmospheric condition aiming to obtain the expected phase of graphene. After heat treatment, an additional special treatment was given, where sample was then rinsed with distilled water. Furthermore, the heated coconut shell was characterized by Raman Spectroscopy (785 nm) and X-ray diffractometry. Based on the treatment and characterization conducted, all samples were likely to contain reduced graphene oxide (RGO) phase.The XRD data have supported the existence of RGO with the diffraction peak position (2q) at 25o and 45o. Evidence is also given by the result of Raman Spectroscopy which produces peaks (denoted by D and G bands) located at wave numbers of 1300 cm-1 and 1590 cm-1. The value of the ratio ID/IG of the two samples in the figures are 2.6 and 2.51 (matched with ratio ID/IG of RGO). The ID/IG ratio of sample which was rinsed by distilled water is higher that those without rinsing treatment.
Characterization of Al-Si-Mg/Al2O3 Nanocomposite Produced by Stir Casting Method
Authors: Zulfia Anne , Salahuddin J. , Ahmad Hafeizh E.
Published: August 2015

Al-Si-Mg reinforced with Al2O3 nano particles have been made by stir casting method. The vortex produced by stirrer is to distribute the Al2O3 nano particles in the molten aluminium. The volume fraction of Al2O3 nano particles was varied from 0.5, 1, 2, 3, to 5 Vf%, while the addition of magnesium was 3 Vf% as wetting agent to improve the wettability between Al2O3 nano particle and Al-Si-Mg matrix. The effect of Al2O3 on characteristic of Al-Si-Mg composites was studied. It is found that the presence of Al2O3nano particle led to significant improve in mechanical properties, especially at addition of 0.5 Vf% Al2O3. The ultimate tensile strength reached to 154 MPa with 10.24 % elongation, while the hardness reached to 37.7 HRB followed by decrement in wear rate. The porosity level tend to increase with increasing of Al2O3 and caused decrement in mechanical properties.
Fe-Si-Al Alloys Prepared by a Spark Plasma Sintering Technique
Authors: Sudiro Toto , Thosin Kemas Ahmad Zaini , Aryanto Didik , Wismogroho Agus Sukarto , Kurokawa Kazuya
Published: August 2015

Fe-Si alloys with various concentration of Al (0, 1, 3 and 5 % by mass) were synthesized by a spark plasma sintering technique. The specimens were prepared in an evacuated chamber of less than 4 Pa and under compressive stress of 40 MPa. During spark discharge, the heating rate was fixed at 10°C/min. After the SPS process was completed, the specimen surfaces were ground with silicon carbide papers. The metallographic characterization was performed by mean of X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy. According to sintering curves, all samples seem to have a similar sintering behavior. The densification of specimens was completed in the temperature range of about 1020-1050°C. Microstructure and phase characterization revealed that the alloys were mainly composed of FeSi2 and FeSi phases containing oxide inclusions. The SEM images indicated that the fraction of FeSi phase and oxide inclusions appears to decrease with increase in Al concentration in the Fe-Si alloy.
Synthesis of Amylopectin Macro-Initiator for Graft Copolymerization of Amylopectin-g-Poly(Methyl Methacrylate) by ATRP (Atom Transfer Radical Polymerization)
Authors: Handayani Aniek S. , Purwaningsih Is Sulistyati , Chalid Muhamad , Budianto Emil , Priadi Dedi
Published: August 2015

Graft copolymer of Amylopectin and PMMA was synthesized by atom transfer radical polymerization (ATRP) method. The hydroxyl groups of amylopectin partially substituted with tert-butyl a-bromoisobutyrate to form tert-butyl a-bromoisobutyrate (TBBiB ) groups. This compound is known as an efficient macro-initiator for ATRP process. This research, aimed to obtain a bio based polymer of Amylopectin, in which the amylopectin was used as macro-initiator in the ATRP of MMA. The experiment was carried out in the homogeneous system under temperature range of 40 – 70°C in DMSO solution using TEA as catalyst. The modified amylopectin-TBBiB then was grafted to methyl methacrylate trough ATRP. Product characterization indicates that the graft copolymer Amylopectin-g-PMMA is efficient and the obtained product owns well defined structures
Preparation of Zn-ZrO2 Nanocomposite Coating by DC and Pulsed Current Electrodeposition Technique with Low Current Density
Authors: Setiawan Asep Ridwan , Noorprajuda Marsetio , Ramelan Aditianto , Suratman Rochim
Published: August 2015

In the present work, Zn-ZrO2nanocomposite coatings were deposited on the copper substrate through DC and pulse electrodeposition technique with low current density (10 mA/cm2). The effect addition of ZrO2nanoparticles and pulse current were studied. The surface morphology, microhardness and erosion resistance of Zn-ZrO2nanocomposite coating were evaluated. The result shows that, with the addition of ZrO2particles, the surface morphology of Zn-ZrO2nanocomposite coating was smoother. Phase identification by XRD confirm that Zn layer had been sucessfully deposited. The presence of ZrO2nanoparticles was not detected. Compared to DC, pulsed current electrodeposition technique showed higher cathodic efficiency, better microhardness and good erosion resistance.
Electronic Structure of Muonated Me4P[Pd(dmit)2]2
Authors: Sulaiman Shukri , Ahmad S.N.A. , Mohamed-Ibrahim M.I. , Watanabe Isao
Published: August 2015

Me4P[Pd(dmit)2]2 is an organic magnet that show long range antiferromagnetic ordering as indicated by Muon Spin Rotation measurements. Three muon centers were observed in the material. To determine the muon stopping sites, we have employed the Molecular Orbital Cluster Method to study the electronic structure of muonated Me4P[Pd(dmit)2]2. We used a cluster containing 1 formula unit in our investigations and applied the Density Functional Theory method. Three µ+ centers in the vicinity of three chemically non-equivalent sulfur sites, namely thione, thiol and thiolate were examined. All three µ+ sites were found to be energetically stable. In the pure Me4P[Pd(dmit)2]2 cluster, the spin densities of the doublet state system is spread throughout the entire dimer. Spin density of only about 0.13 is localized around the thiolate moiety. For all three µ+ centers, the lattice relaxation effect is important to stabilize the sites energetically.
Preparation, Characterization and Photocatalytic Activity of Multifunctional Fe3O4/ZnO/CuO Hybrid Nanoparticles
Authors: Taufik Ardiansyah , Kalim Iqriah , Saleh Rosari
Published: August 2015

A series of copper oxide supported on Fe3O4/ZnO with molar ratio of Fe3O4:ZnO:CuO varies from 1:1:1 to 1:1:5 were prepared by sol-gel method. X-ray diffraction, field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and vibrating sample magnetometer were used to characterize the as prepared Fe3O4/ZnO/CuO hybrid nanoparticles. The results show that Fe3O4/ZnO/CuO hybrid nanoparticles consist of cubic spinel Fe3O4, hexagonal wurtzite ZnO and monoclinic CuO. All prepared samples show ferromagnetic behavior. The photocatalytic activities of these hybrid nanoparticles under visible light irradiation were evaluated by the degradation of malachite green. The results revealed that hybrid nanoparticles exhibited higher photocatalytic activities than pure nanoparticles.
Effect of Soaking Time in Alkali Solution on the Interfacial Shear Strength of Cantala Fiber/Recycled HDPE Composites
Authors: Wijang Wisnu R. , Sukanto Heru , Anwar Miftahul
Published: August 2015

The interfacial shear strength (IFSS) between natural fibers and thermoplastics matrix is one of the key parameters to increase the mechanical properties of composites. IFSS can be improved by alkali treatment. Therefore, the research is to investigate the influence of IFSS soaking time in alkali solution of cantala fiber/Recycled High Density Polyethylene (RHDPE) composites. Experimentally, cantala fiber/RHDPE composites were manufactured by simple hot press machine. Alkali treatment on the surface of cantala fibers was carried out on 2% sodium hydroxide (NaOH) solution for a period time, i.e., 0, 4, 8, 12, 16, 20, and 24 hours. The IFSS value of composites was observed using single fiber pullout test method. The result shows that the increase of soaking time in alkali solution could improve IFSS of cantala fiber/RHDPE composites by 43%.
Electrospun Polyvinylpyrrolidone as a Carrier for Leaves Extracts of Anredera cordifolia (Ten.) Steenis
Authors: Nuryantini Ade Yeti , Edikresnha Dhewa , Munir Muhammad Miftahul , Khairurrijal
Published: August 2015

Nanofibers produced by electrospinning method have high porosity, large surface area, long size, and their dimensions are ranging from nanometers to micrometers. The synthesis process was straightforward, uncomplicated and it can be processed from various type of materials and the nanofibers can be used as drug release. The polymer matrix acts as a carrier of other materials that will be spun. The purpose of this study was to to prepare electrospun fiber mats and to incorporate extracts from the leaves of Anredera cordifolia (Ten.) Steenis plant (Binahong). Polyvinylpyrrolidone (PVP) was used as a carrier matrix. Binahong leaf extract was added to a solution of PVP. The solution was then electrospun using a single nozzle and drum collector system under condition of voltage 12.5 kV, nozzle collector distance of 12 cm, and flow rate 10 μl /minute. In this study, the composite of Binahong extract and PVP solution was succesfully made into nanofiber.
Fabricating Polyvinyl Alcohol Fibers with Evenly Distributed Nano Silver
Authors: Harsojo  , Layla Anna , Triyana Kuwat , Sosiati Harini
Published: August 2015

Fabrication of polyvinyl alcohol (PVA) fibers loaded with evenly distributed nanosilver has been sucessfully done using electrospinner. The electrospinner is set at 15 kV DC voltage with distance between electrodes 13 cm, using a syringe hole diameter 0,5 mm. The feeding solution for the electrospinning was prepared by directly mixing the solution of PVA in water with a stable colloid of nanosilver at room temperature. The fibers morphology was characterized using scanning electron microscope. The optical property was tested using spectrometer. The distribution of silver nanoparticles in the fibers was tested using transmission electron microscope. The result indicates that the fibers still showing plasmonic property of silver having peak at 410 nm with no crystaline changes. The diameter of fibers loaded with nanosilver are smaller compared to that of the ones without nanosilver.The distribution of nanosilver in fibers made of PVA and the ones made of PVA and chitosan are compared and discussed.
Analysis of the Cold Compaction Behaviour of TiH2-316L Nanocomposite Powder Blend Using Compaction Models
Authors: Machio Christopher , Machaka Ronald , Shabalala Thembinkosi , Chikwanda Hilda Kundai
Published: August 2015

The paper captures the effect of structure and the applicability of compaction models using the cold compaction of a TiH2-SS316L composite powder prepared by high energy mechanical milling. The composite blend was cold pressed uniaxially to pressures of up to 1250MPa. The compressibility of the composite blend was evaluated by fitting the experimental data to the most commonly used compaction models of Heckel, the Kawakita-Lüdde, the Cooper-Eaton, the Ge, and the Panelli-Filho compaction equations. Among the models, the Kawakita-Lüdde and Cooper-Eaton models fitted the experimental data very well with a good correlation (the correlation coefficient greater than 0.99) throughout the entire pressure range under investigation. The nature and mechanisms responsible for the densification during cold compaction are discussed. The Heckel, Ge, Panelli-Filho, and Cooper-Eaton model analysis showed that the dominant compaction mechanisms for composite blend were rearrangement of particles followed by elastic and plastic deformation. The results are discussed by way of a comprehensive model intercomparison study of the cold compaction behaviour using existing models.
Effect of Processing Parameters on the Properties of Metal Injection Moulded Titanium Dental Implants
Authors: Sidambe Alfred T. , Todd Iain , Hatton Paul
Published: August 2015

Metal injection moulding (MIM) is a well-established, cost-effective method of fabricating small-to-moderate size near net-shape metal components. MIM is increasingly being employed as a process for fabricating orthopaedic and dental products with complicated shapes. In this study, commercially pure titanium (CP-Ti) powder has been used to fabricate dental implants via MIM. The CP-Ti powder was mixed with binders containing Polyethylene glycol (PEG), High Density Polyethylene (HDPE) and stearic acid (SA) to form the MIM feedstock. Commercially available feedstock was also used to fabricate MIM implants. The MIM compacts were then subjected to debinding and sintering, and then the mechanical and chemical properties of the compacts were investigated for their suitability for dental implantology. The effect of the MIM processing variables on the surface roughness of CP-Ti was also investigated and studies for biocompatibility were carried out using in-vitro cell culture. The results showed that the mechanical and chemical properties of the sintered components were within ASTM Grade MIM 2 and Grade MIM 3 (ASTM F2989 − 13) specifications for titanium. The results also showed that the implants produced by MIM appeared to meet basic biocompatibility requirements. It was concluded that dental implant prototypes may be fabricated successfully using MIM and this approach offers greater opportunities for future manufacturing.
Challenges and Solutions in the Development of Magnesium Sheet for Sustainable Vehicle Concepts
Authors: Kainer Karl Ulrich , Hoppe Roland , Bohlen Jan , Kurz Gerrit , Yi Sang Bong , Letzig Dietmar
Published: August 2015

Magnesium as the lightest structural metal offers significant potential weight saving compared with steel and aluminium. Cast magnesium components are widely used, e.g. as engine blocks or gear box housings. To open more opportunities for weight saving, it is necessary to widen the application fields to wrought products, such as large thin walled components for which sheets as semi-finished products are needed. The production and processing of magnesium sheets material is currently hampered by the limited formability of magnesium and high costs. The use of the twin-roll casting (TRC) as a cost-effective manufacturing process and the development of new calcium-containing alloys are leading to a decisive reduction of those obstacles.
Fabrication of Iron-Base Shape Memory Alloy Fiber Reinforced Aluminum by Spark Plasma Sintering
Authors: Komiya Yoshiki , Nabeshima Fumihiko , Izui Hiroshi
Published: August 2015

Aluminum was composited with iron-base shape memory alloy (SMA) fiber. It is important to join between matrix metal and reinforced SMA fiber successfully. Matrix metal can obtain compressive residual stress caused by shape memory effect of SMA fiber without strong interface. In this study, aluminum matrix composite reinforced by iron-base SMA fiber was fabricated by Spark Plasma Sintering (SPS). At this method, sintering of hard-to-sinter materials (Al and Ti), junction of flame bonding materials is easy. The pure aluminum powder with iron-base SMA fiber was joined at 773K. As a result, intermetallic phase was formed at the interface between aluminum and iron-base SMA fiber and it was clarified that the interfacial strength depends on kind and thickness of intermetallic phase. This strong interface gives beneficial residual stress into aluminum from SMA fiber.
Kinetics of Titanium Metal Injection Moulding Feedstock Thermal Debinding
Authors: Machaka Ronald , Chikwanda Hilda Kundai
Published: August 2015

Controlled thermogravimetric pyrolysis of a metal injection moulding (MIM) feedstock was performed in order to characterize the associated thermal debinding processing in an inert atmosphere. The feedstock was formulated using Ti-6Al-4V metal powders and a newly developed MIM binder system. The catalytic effect of the metal powder on the decomposition of the binder components in the MIM feedstock is observed. The thermogravimetric analysis also reveals that thermal debinding is characterized by a multistage degradation behaviour of the binder system. In order to determine the kinetic parameters of the degradation step Ozawa and Ozawa-Flynn-Wall methods were applied. Activation energies with the degree of thermal debinding are deduced and discussed in terms of the decomposition of the binder components in the MIM feedstock.
Reinforcement of 2124 Al Alloy with Low Micron SiC and Nano Al2O3 via Solid-State Forming
Authors: Gxowa Zizo , Camagu Sigqibo Templeton , Govender Gonasagren , Filipe Pereira Manuel
Published: August 2015

A powder metallurgical process was used to fabricate Metal Matrix Composites (MMCs). A 2124 aluminium alloy was reinforced with 5 and 10 vol.% of Al2O3(40-70nm) to form Metal Matrix Nano Composites (MMNCs) as well as 10 and 15 vol.% of SiC (1-10µm) to fabricate low micron MMCs. It was observed that the nano-sized Al2O3particles were evenly dispersed in the aluminium matrix while a lot of loose SiC particles settled on the grain boundaries in the low micron MMCs. The relative density of all the composites increased due to sintering, however full densification was not achieved. This result was attributed to the hindered motion of dislocations, grains and grain boundaries by reinforcing particles. The 2124-Al/10%-SiC composite was cold extruded and the extruded part fractured. A metallographic evaluation was carried out and it was deduced that the mode of failure was intergranular cracking. Hardness tests performed after sintering indicated that hardness increased with an increase in volume fraction of reinforcement in the matrix. Annealing of the extruded part resulted in a decrease in hardness.
Influence of Quench Rate on the Artificial Ageing Response of an Al-8Si-0.4Mg Cast Alloy
Authors: Sjölander Emma , Seifeddine Salem , Fracasso Federico
Published: August 2015

The aim of the study is to present the influence of quench rate on the artificial ageing response of Al-8%Si-0.4%Mg cast alloy in terms of Brinell hardness and yield strength. The investigated material was produced by a gradient solidification technique and exhibited a microstructure that corresponds to the one of gravity die castings, with a dendrite arm spacing of approximately 25 µm. The study comprises two solution treatment temperatures, five quench rates and artificial ageing times exceeding 100 hours at 170 and 220 °C. The microstructure and concentration profiles of Mg and Si were evaluated using energy and wavelength dispersive spectroscopy. Microstructural examination reveals an increment of solutes in the Al-matrix when higher solution treatment temperatures accompanied with high quench rates are applied and shows how both Si and Mg atoms have diffused towards the eutectic during quenching. Consequently, i.e. by increasing the levels of solutes and vacancies, the highest strength levels were realized. The study confirmed that quench rates above 2 °C /s do not offer substantial strength improvement while quenching at lower rates resulted in a lower peak hardness and longer times to peak
Phase Transformation Cycle β→ α′ + α + α"→ β in Ti6Al4V Alloy
Authors: Mutombo Kalenda , Charles Siyasiya , Stumpf Waldo
Published: August 2015

The β-phase transforms to α′, α and α" within a range of temperature from the β-transus (Tβ) to about 600°C, considering no external stress is applied. Two types of microstructure were obtained: acicular martensite when rapidly cooled and lamellar α/β when slowly cooled from the β phase field. The sequential transformation of β into α′, α-phase, α2, and α" was revealed as peaks on the coefficient thermal expansion (CTE) curves, however, reversed transformations: α"→β, and α→β, were revealed by the DSC thermograms. The presence of β, α′, α, α2 and α" was identified by means of XRD analysis and HRTEM.
Static Recrystallization Characteristic of Low Temperature Rolled AZ31 Magnesium Alloy during Annealing
Authors: Su Jing , Sanjari Mehdi , Kabir Abu Syed , Jung In Ho , Yue Steve
Published: August 2015

Microstructure evolution and static recrystallization kinetics of a magnesium AZ31 alloy during annealing have been investigated. The Mg alloy sheets were rolled at 100°C at a low rolling speed of 15m/min and a high rolling speed of 1000m/min to reductions of 8%, 23% and 30%. Annealing was then conducted on the as-rolled specimens at 200°C for different times. The microstructure was characterized by optical microscopy and recrystallization kinetics were evaluated by means of Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The softening behavior was found to be divided into two annealing stages. The first stage was related to the recrystallization on high stored energy regions, such as shear bands and twins, while the second stage was associated to the recrystallization of low stored energy areas.
Age-Hardening Response of Mg-Al-Sn Alloys
Authors: Humaun Kabir Abu Syed , Su Jing , Sanjari Mehdi , Jung In Ho , Yue Stephen
Published: August 2015

Precipitation hardening has been used before as one of the most effective strengthening methods for many metallic alloys. However, this method has not been studied completely in magnesium alloys, and the numbers of precipitation hardenable wrought Mg alloys are still very limited compared to aluminum alloys and steels. The age hardening responses of Mg-Al-Sn alloys in cast-homogenized condition were investigated by isothermal aging at 200°C for prolonged time. It was found that hardness can be improved significantly for the alloy with higher amounts of tin. The improvement in hardness was reasoned by the formation of precipitates. The shapes and morphology of the precipitates were different depending on the orientations of the grains. The precipitates were characterized by scanning electron microscope.
Diamond Insert Wear when Turning Rapidly Solidified Aluminium RSA 443 of High-Silicon Content
Authors: Mkoko Zwelinzima , Abou-El-Hossein Khaled
Published: August 2015

Rapid solidification of molten metals has been recently used to generate a new group of alloys having ultra-fine microstructures and high end mechanical properties. Therefore, such alloys can be successfully used in the optics industry to produce diamond machined mirrors and mould inserts for plastic lens injection. Rapidly solidified aluminium grades characterised by their ultra-fine grains can be used to replace traditional optical aluminium such as 6061-T6 which has coarse microstructure when making optics. However, there is currently no data available on the performance of these new grades in terms of diamond tool wear when machined in single-point diamond turning operation. This paper reports on the wear mechanisms of natural diamond tools when turning RSA 443 which is a new aluminium grade produced by rapid cooling process. Although this new aluminium grade enjoys fine microstructure, it is harder than traditional optical aluminium because of its increased content of silicon (about 40%). Therefore, there is a need to establish a deeper understanding of diamond tool performance when using diamond turning of optical components from this material. In this study, three machining parameters, namely cutting speed, feed rate, and depth of cut, were varied at three levels and the edge wear of the diamond inserts was observed using scanning electron microscopy after 4 km of cutting distance. The first observations from this preliminary study show that tool wear of diamond is more sensitive to the change in cutting speed than it is for other cutting parameters. Wear is relatively high (12 µm) at the lowest cutting speed (500 rpm). However, at high cutting speed (3000 rpm) the edge wear was small (3 µm). This could be attributed to the increased impacts of cut the material on the cutting edge. The study also reports on the surface finish obtained at the different combinations of cutting parameters.
Dry Sliding Wear Behavior of EB Surface-Alloyed and Dispersed AZ91 Magnesium Alloy under Mild Wear Conditions
Authors: Fritzsch Katja , Buchwalder Anja , Zenker Rolf
Published: August 2015

This paper reports on investigations of the beneficial effects of electron beam alloying (EBA) and electron beam dispersion alloying (EBDA) on the wear behavior of AZ91D Mg alloy under mild wear conditions with applied normal loads of 1…10 N. The layers generated had a thickness of 1.5 mm with Al contents of 30 wt.%. For dispersion alloyed layers, TiC was added with particle sizes of 20…100 µm. At a sliding distance of 20 m, the wear rates of alloyed layers (150 HB) and dispersion alloyed layers (180 HB) were almost the same and could be reduced by half compared to the untreated AZ91D (60 HB). Due to their large size and the large spaces between them, TiC particles were pressed into the layer matrix, or were torn out and acted as additional abrasives. Therefore, at a sliding distance of 50 m, the wear rate of dispersion alloyed layers increased to the level of the base material.
Twinning Assisted Crack Propagation of Magnesium-Rare Earth Casting and Wrought Alloys under Bending
Authors: Maier Petra , Mendis Chamini , Wolff Martin , Müller Sören , Hort Norbert
Published: August 2015

Due to their high specific strength, good corrosion resistance and high temperature strength Magnesium alloys containing Rare Earth additions are promising candidates for structural and engine applications in the transportation industry. Also medical applications, like bone screws and nails, benefit from their moderate corrosion rate and biocompatibility. All applications need materials which show a high strength, ductility and fracture toughness in case a crack has formed during service to keep safety against rupture. In this study four extruded Mg10Gd based alloys modified with Nd and La have been 3-point-bend tested at low a deformation speed to evaluate the influence of the microstructure on crack growth. A comparison to the cast material (subjected to T4 to increase ductility and to reduce the dendritic microstructure) shows an increase in strength and ductility due to the fine grained microstructure as a result of recrystallization during extrusion. The maximum bending strength and outer strain to crack initiation is also strongly influenced by the alloying system itself. The influence of Nd and La to the binary alloy Mg10Gd is discussed in using tensile, compression and bending tests. The increase in strength results in reduced elongation to fracture in tension loading as well as the outer strain for the crack initiation during bending tests. Tensile tests are often discussed to be not a reliable method for determining the Young’s modulus of magnesium. Therefore resonance frequency damping analysis has been applied to determine the dynamic modulus of elasticity, which is compared with the flexural (bending) modulus. Crack growth is discussed using light microscopy and correlated with bending stress-strain curves. The crack growth rate of the extruded, fine grained material is many times higher than of the cast, coarse grained material. Crack propagation is mostly transgranular and assisted by twinning.
Tribocorrosion Response of Laser Clad TiNiZrO2 Composite Coatings on Ti6Al4V
Authors: Obadele Babatunde Abiodun , Andrews Anthony , Olubambi Peter Apata , Mathew Mathew Thoppil , Pityana Sisa
Published: August 2015

The design of tribocorrosion resistant composite on Ti6Al4V alloy by laser surface cladding of admixed metal-ceramic powder was successfully achieved using a 2 kW CW ytterbium laser system (YLS). The effects of TiNiZrO2 addition on the tribocorrosion properties of the synthesized composite coatings were investigated in 1 M H2SO4 solution using open circuit potential and potentiodynamic polarization techniques. The experimental results showed that TiNiZrO2 refined the microstructure to flower-like structure. A strong metallurgical bond was obtained between the coatings and the Ti6Al4V alloy substrate with inter-columnar widmansttaten α΄ grains at the interface. There was a significant increase in surface microindentation hardness values of the clad layers. Also, the presence of zirconia shifted the tribocorrosion potential to more noble values and significantly enhanced the tribocorrosion resistance of the composites.
Twin-Roll Casting after Intensive Melt Shearing and Subsequent Rolling of an AM30 Magnesium Alloy with Addition of CaO and SiC
Authors: Dieringa Hajo , Das Sanjeev , Eskin Dmitry , Fan Zhong Yun , Katsarou Lydia , Horstmann Manfred , Kurz Gerrit , Mendis Chamini , Hort Norbert , Kainer Karl Ulrich
Published: August 2015

Intensive melt shearing is a process that can be used for mixing ceramic particles into magnesium melt. It applies shear stress to the melt and can de-agglomerate nanoparticle additions to magnesium melts without the use of electromagnetic fields or ultrasound. A wrought magnesium alloy AM30 was selected for processing with intensive melt shearing and subsequent twin-roll casting. AM30 with additions of CaO and SiC were also processed by this route and the hardness and microstructure were investigated. Sheets were rolled and their tensile strength was determined. The work was done as part of the European Union research project ExoMet. Its target includes the production of high-performance magnesium-based materials by exploring novel grain refinement and nanoparticle addition in conjunction with melt treatment by means of external fields.
Bio-Mechanical Compatibility Assessment of Titanium-Nickel Alloy Fabricated Using Cold Spray Process
Authors: Hamweendo Agripa , Moloisane Lebogang , Botef Ionel
Published: August 2015

This paper presents the bio-mechanical compatibility assessment of Titanium-Nickel (TiNi) alloy fabricated using cold spray (CS) process. This research creates opportunity for meeting the increased demand for biomedical implants in orthopedic surgeries brought by sport and traffic related bone injuries. Due to their exceptional properties, TiNi alloys are promising alternative biomedical materials to the traditional Ti6Al4V alloys. Studies show that the conventional methods for producing TiNi alloys have several challenges. As a contribution towards resolving this problem, this paper studied the bio-mechanical properties of Ti and TiNi structures fabricated using CS process. The results of this study show that the porosity, incipient Young’s modulus, and tensile strength of TiNi and Ti coatings are close to the required values for the biomedical implants. Consequently, this research demonstrates that porous TiNi and Ti structures fabricated by CS are possible candidates for biomedical implants and that CS could be a new process for fabricating near-net shape bio-mechanical compatible materials.
Direct-Chill Casting of AA7449 Aerospace Alloy under Electromagnetic and Ultrasonic Combined Fields
Authors: Haghayeghi Reza , Kapranos Plato
Published: August 2015

This work is based on investigation of the influence of electromagnetic fields and ultrasonic vibrations and their combination on the resulting microstructure of an AA7449 aerospace aluminium alloy. The results demonstrate the application of the compound electro-magnetic and ultrasonic fields under optimum conditions delivers not only a refined microstructure but also consistent distribution of chemical composition. It suggests an alternative method for producing high strength aerospace alloys which could not be refined through conventional addition of chemical grain refiners.
Effect of Solidified Structure on Hot Tearing in Al-Cu Alloy
Authors: Yoshida Yasuyuki , Esaka Hisao , Shinozuka Kei
Published: August 2015

Hot tearing is the one of the biggest problems when casting aluminium alloys. Although there has been much research work in this field, it is still not clear what causes hot tearing and how it propagates. Furthermore, the effect of solidified structure on the hot tearing has not been clear. Therefore, this study has been carried out to correlate the solidified structure and hot tearing. Al-2.0 wt% Cu alloy was used for test alloy. To change the solidified structure, some amount of refiner was added to the molten alloy. A permanent mould, which has been developed by us, can form hot tearing intentionally in the center region of a solidified shell. The cross section of a solidified shell was metallographically investigated and solidified structure and hot tearing were characterized. The length of hot tear decreased with increasing the amount of refiner. This may indicate that it is difficult for hot tear with fine equiaxed grains to propagate. In addition to this, the residual liquid around the hot tear was moved to the cracking due to negative pressure and hot tearing was partially healed.
Massive ice and icy sediments throughout the Tuktoyaktuk Peninsula, Richards Island and nearby areas, District of Mackenzie
Authors: Rampton V , Mackay J R
Published: August 2015

Massive bodies of subsurface ice and icy sediments are relatively abundant throughout the Tuktoyaktuk Peninsula, Richards Island, and nearby areas. A statistical study, based upon shot hole records, shows that massive ice is most common at a depth of about 40
feet. Icy sediments, where present, occur with relatively constant frequency to a depth of at least 140 feet. At Tuktoyaktuk, examples of massive ice and icy sediments are readily accessible for examination in man-made excavations and coastal exposures.
Genesis 2–3 and Alcibiades’s speech in Plato’s Symposium: A cultural critical reading
Authors: Dafni Evangelia G.
Published: August 2015

The purpose of this article is to discuss some basic problems and methodological steps concerning the encounter between Hebrews and Greeks in the Classical period and its impact on the Hellenistic era. The relationship between the Old Testament and Ancient Greek literature will be examined on the basis of Genesis 2–3 and Alcibiades’s speech in Plato’s Symposium (212c–223d). The following considerations and models of interpretation can arise from the analysis of Alcibiades’s speech compared to M- and LXX-Genesis 2–3: (1) Ancient Greek writers were familiar with Old Testament oral or written traditions through improvised translations. They prepared the way for the LXX and, in their compositions, were in dispute with them although they do not make specific references to the Hebrews and their literature; (2) Hebrew authors knew the works of Ancient Greek authors and used Greek philosophical terminology which they creatively adapted to Semitic models; (3) Both models are possible. One should not rush to any decisions but examine each case individually, in the original language.
A comparative evaluation of the effectiveness of erbium-doped yttrium aluminum garnet laser with other in house refurbishing methods for reconditioning stainless steel and ceramic brackets. An environmental scanning electron microscope and shear bond strength analysis: An in-vitro study
Authors: Devjee Nimay , Deshmukh Sonali V. , Jethe Sandeep , Naik Charudatta R.
Published: August 2015

Introduction

Brackets can be recycled by sending them to a commercial recycling company but it is time consuming and the bracket cannot be bonded in the same appointment. Hence in-house methods for recycling of brackets would be beneficial to both the orthodontist and the patient.

Aim

In our study, we compared the shear bond strength of brackets after being recycled with erbium-doped yttrium aluminum garnet (ER:YAG) laser, sandblasting and the thermal method.

Materials and Methods

The study was carried out on 126 extracted premolars. The bonding procedure was performed with mandibular premolar metal and premolar ceramic brackets. Eighty-four teeth were subdivided into three groups for each method of recycling. These groups were further subdivided into two groups of 14 teeth each for the types of brackets used. Prior to the initial bonding the bracket was also viewed under an environmental scanning electron microscope to examine the meshwork of the brackets and once again after the respective recycling methods had been performed.

Results

We found that for stainless steel brackets, the sandblasting method was superior to the ER:YAG laser, as the recycled brackets showed a higher shear bond strength. For ceramic brackets the ER:YAG laser recycled group had the highest recycled shear bond strength therefore was the best method of recycling ceramic brackets.
Simple and cost-effective approach for maxillary bilateral posterior intrusion: Nandlal Toshniwal Rural Dental College double intrusion arch
Authors: Baheti Mayuresh J. , Gharat Ninad V. , Toshniwal Nandlal Girijalal
Published: August 2015

Prosthodontic rehabilitation of edentulous space is often complicated with overeruption of antagonistic tooth and often requires preprosthodontic intervention. In this context, orthodontic intrusion of the overerupted antagonistic tooth to facilitate prosthodontic rehabilitation is a desirable strategy. Without orthodontic molar intrusion or segmental surgical impaction, restoring the posterior occlusion often entails the need for significant reduction of maxillary molar crown height, with the potential need for costly iatrogenic root canal therapy and restoration. Conventional orthodontic techniques do not intrude posterior teeth effectively, and almost all methods result in anterior extrusion rather than posterior intrusion. This case report describes the treatment of a patient with supra-erupted maxillary right and left first molars intruded with Nandlal Toshniwal Rural Dental College double intrusion arch. The results showed that the biological responses of the teeth and the surrounding bony structures to the intrusion appeared normal and acceptable.
Three-dimensional canine loop for management of buccally erupted canines
Authors: Mehrotra Praveen , Bhagchandani Jitendra , Agarwal Sonahita , Thukral Anchit
Published: August 2015

Maxillary canines are known as the cornerstones of mouth. They are considered to be important for esthetics and for functional occlusion. Any disturbance in the eruption process leading to an aberrant position will hamper esthetics as well as function. Orthodontic tooth movement of total buccally blocked-out canine is usually difficult as it is related with the problems of severe crowding, midline deviation, involvement of long root movement and risk of gingival recession. Such conditions can be treated orthodontically in various ways, but this clinical innovation helps to correct the buccally placed canines into the arch with a precise control of the canine in all the Three-dimensions (3D) of space as well as providing maximum comfort to the patient by placing the canine loop on the palatal surface of the tooth, reducing soreness on the labial mucosa. It can be easily fabricated and activated at chairside for either simultaneous or sequential control in 3D.