bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Ginger Extract Performance as Corrosion Inhibitor in Acid and Neutral Environments
Authors: Kurniawan Budi Agung , Pradana Andhi , Sulistijono Sulistijono , Sutarsis Sutarsis
Published: February 2014

Study about organic inhibitor has been performed to analyze effect of ginger extract concentration (Zingiber officinaler) to corrosion characteristic of API 5L grade steel under 3.5% NaCl and 0.1M HCl. Amount of 100 to 500 ppm inhibitor injected into each solution and electrochemistry tests were performed. Ginger extract has been prepared previously with maceration method and tested with FTIR to identify type compound in it. Tafel test result showed that corrosion rate of steel decreased in accordance with the increase of inhibitors concentration. Corrosion rate decreased to 12.13 mpy at 500 ppm inhibitor under NaCl solution, with efficiency 54.79%. While in HCl, corrosion rate showed similar trend, with corrosion rate 8.19 mpy at 500 ppm, with efficiency 81.66%. EIS result showed that impedance increased with the increase of inhibitors concentration, while FTIR result showed that ginger extract inhibitor contain 2-Methoxy-4-propylphenol which is known as antioxidant compound. According to XRD test, Fe2O3 and Fe3O4 compound were identified on steel surface. Ginger extract might worked better in acid environment since it decrease corrosion rate significantly compared to neutral solution.
Ohmic Contact in P-HEMT Wafer Using Metallization with Ge/Au/Ni/Au
Authors: Dolah Asban , Abd Hamid Muhammad Azmi , Deraman Mohamad , Yusof Ashaari , Ngah Nor Azhadi , Muhammad Norman Fadhil Idham
Published: February 2014

In this study, Ohmic contact were fabricated on AlGaAs HEMTs structure. A good metal-semiconductor interface are essentially for achieving lower specific contact resistance. An AlGaAs epi wafer was supply by the vendor. AlGaAs substrate was cleaned using wet chemical etching. Electrodes were fabricated through a sequenced of lithography, cleaning, sputtering and lift-off processes. The electrodes were made with metal layers of Ge, Au and Ni. Parameters such as metal thickness, annealing temperatures (from 300°C to 400°C) and annealing time were varies during fabrication process. Electrical characterizations after annealing are carried out using transmission line method (TLM) to obtain the specific contact resistance. Annealing temperature between 340°C to 360°C produced contact resistance below 5 x 10ˉ³Ω/cm-2.
Possible Existence of the Stripe Correlations in Electron-Doped Superconducting Cuprates Eu1.85Ce0.15Cu1-yNiyO4+α-δ Studied by Muon-Spin-Relaxation
Authors: Risdiana Risdiana , Safriani Lusi , Somantri Wahyu Alamsyah , Saragi Togar , Adachi Tadashi , Kawasaki Ikuto , Watanabe Isao , Koike Yoji
Published: February 2014

Partially Ni-substituted electron-doped superconducting cuprates of Eu1.85Ce0.15Cu1-yNiyO4+α-δ (ECCNO) with y = 0, 0.01, 0.02 and 0.05 have been studied by muon-spin-relaxation (mSR) measurements, in order to elucidate whether or not the dynamical stripe correlations of spins and charges exist in electron-doped cuprates. It has been found that the development of the Cu-spin correlation is induced at low temperatures through the Ni substitution and that, for y = 0.02, a muon-spin precession due to a long-range magnetic order has been observed at 10 K. These results suggest a possibility that the stripe model can globally explain the high-Tc superconductivity in both hole- and electron-doped cuprates.
Carbon Dioxide Permeation Characteristics in Asymmetric Polysulfone Hollow Fiber Membrane: Effect of Constant Heating and Progressive Heating
Authors: Bin Azhari Muhamad Azwar , Binti Omar Nooririnah , Mustafa Nuzaimah , Ismail Ahmad Fauzi
Published: February 2014

This paper reports the effect of constant heating and progressive on carbon dioxide permeation characteristics in asymmetric hollow fiber polysulfone membranes. Glassy polymers are easily plasticized with the presence of plasticizing agents such as carbon dioxide. Constant heating were applied to the membranes to suppress CO2 induced plasticization. Membranes treated with constant temperature heating exhibits lower pressure-normalize flux for both carbon dioxide and methane compared to untreated membranes. This was probably due to densification of membrane skin layer during heating process. Denser skin layer increases the resistance in the membrane which resulted in decreased of pressure-normalize flux. A higher density of membrane skin layer was achieved by progressive temperature heat treatment. This further increased the resistance in the membrane resulted in a lower value of pressure normalized-flux. With the application of different feed pressure, an almost linear value of CO2 pressure-normalize flux shows that plasticization is successfully suppressed by heat treatment. From the results provided in this study, it can be concluded that plasticization of polysulfone hollow fiber membrane is successfully suppressed by heat treatment process.
Magnetoelectric Coupling Phenomena Based on the Changes of Magnetic Properties in Multiferroic Nanocomposite BaTiO3-BaFe12O19
Authors: Suastiyanti Dwita , Soegijono Bambang , Hikam M.
Published: February 2014

Magnetoelectric (ME) coupling effects in multiferroic materials have attracted much attention in recent times because of the intriguing science underpinning this phenomena and being currently intense interest in the implementation of this coupling in an electronic devices. A new multiferroic system comprising of BaTiO3 (BTO) and BaFe12O19 (BHF) has been synthesized as a bulk nanocomposite system in variation of weight fraction of BTO : BHF =1:1, 1:2 and 1:3 and the second sinter temperature was 925°C for 5, 10 and 15 hours. The presence of both phases were confirmed by X-Ray Diffraction (XRD) studies and MPS Magnet Physik EP3 Permagraph L was used to characterize magnetic properties.The morphology and particle size of nanocomposite was characterized by using Transmission Electron Microscope (TEM). No residual phases were identified in the XRD analysis for all parameters confirming the formation of a BTO-BHF composite system. The TEM images show that all samples have particle in nanosize.For weight fraction of BHF until 2 parts there is an increase of intrinsic coersive and magnetization saturation value. If the weight fraction of BHF exceeds from 2 parts, the coersivity and saturation values decrease. Meanwhile in compound of polyvinyl acetate (PVA) and BHF as a compare material, the magnetic properties increase with increasing the content of BHF until 3 parts. From the above results, it presumes that the nanocomposites with weight fraction of BTO : BHF = 1:3 for all time of sintering have ME coupling interaction showing a multiferroic nature. To give evidence of this phenomena, it needs a measurement of ME coupling coefficients for all parameters.
Modeling of Magnetorheological Damper Using Back Propagation Neural Network
Authors: Ubaidillah Ubaidillah , Priyandoko Gigih , Nizam Muhammad , Yahya Iwan
Published: February 2014

This paper presents a new approach to model magneto-rheological (MR) dampers for semi-active suspension systems. The neural network method using adaptive back-propagation learning algorithm real is proposed. The experimental data collected from suspension test machine consist in time histories of current, displacement, velocity and force measured both for constant and variable current. The model parameters are determined using a set of experimental measurements corresponding to different current constant values. It has been shown that the damper response can be satisfactorily predicted with this model.
The Influence of Ni-Doping on Structure and Magnetic Properties of La0.67Ba0.33MnO3
Authors: Ahmiatri Sitti Saptari , Manaf Azwar , Kurniawan Budhy
Published: February 2014

The hole doped manganites of perovskite structure have attracted great interest in the scientific community because of the rich physical behavior. In this work, we report the influence of Ni-doping on structure and magnetic properties of La0.67Ba0.33Mn1-xNixO3 (x = 0, 0.02, 0.04, and 0.06). Four basic materials La2O3, BaCO3, MnCO3, and NiO are mixed with Planetary Ball Milling during 25 hours, then calcinations on 800°C during 10 hours, compacted, and continued with the process of sintering temperature of 1200°C for 2 hours. Samples were characterized using XRD (X-Ray Diffraction) then refinement by GSAS software. Refinement results showed samples with various x = 0 to x = 0.04 are single phase with monoclinic crystal structure, while the sample with x = 0.06 there are variations in two phases namely monoclinic and hexagonal phases. Magnetic properties of materials La0.67Ba0.33Mn1-xNixO3 characterized by permagraph. Hysteresis loops results showed that the samples La0.67Ba0.33Mn1-xNixO3 are soft magnetic materials, with prices declining saturation with increasing value of x in the sample.
Electrospinning of Poly(vinyl alcohol)/Chitosan via Multi-Nozzle Spinneret and Drum Collector
Authors: Nuryantini Ade Yeti , Munir Muhammad Miftahul , Ekaputra Muhamad Prama , Suciati Tri , Khairurrijal Khairurrijal
Published: February 2014

Poly (vinyl alcohol) (PVA)/chitosan nanofibers membranes were successfully prepared by electrospinning employing a multi-nozzle and a drum collector. The use of multi-nozzle and drum collector system is intended to produce stacked nanofibers to form a membrane as a matrix for burn wound healing application. The membranes thickness was controlled by varying applied voltage, flow rate, drum collector rotating speed, and nozzle-collector distance. The electrospinning process and nanofibers formation on the collector was observed using a digital camera. The scaling relationship between current-flow rate and current-voltage for PVA/chitosan fulfills power laws of I ~ Qα and I ~ Eβ, respectively.
Magnetic Properties and Reflection Loss Characteristic of Mn-Ti Substituted Barium-Strontium Hexaferrite
Authors: Repi Viktor Vekky Ronald , Manaf Azwar , Soegiono Bambang
Published: February 2014

The magnetic and microwave absorbing properties of the Mn-Ti substituted barium strontium hexaferrite, Ba0.5Sr0.5Fe12-xMnx/2Tix/2O19 (x: 0; 0.2 and 0.4) prepared by a mechanical alloying technique were investigated. Material phases in synthesized samples were identified by XRD from which results confirmed that the sinthesized material was a single phase material. The hysteresis loop for the samples as analyzed by a permagraph showing those of typical of hexaferrite permanent magnet but with both remanence and coercivity decreased remarkably with the increasing fraction of Mn-Ti. The reflection coefficients S11, S21 of the ferrite samples were measured in the X-band frequency range (9-15 GHz) and their absorbing properties were calculated according to transmission line theory. It was observed that the absorption was taking place in the whole frequency range between 9 and 15 GHz. In addition, resonance frequencies have shifted due to the Mn-Ti substitution in barium-strontium hexaferrite. It is concluded that the Mn-Ti substituted barium-strontium hexaferrites would be a good potential candidate for electromagnetic absorbers and for other practical applications at high frequencies.
Analysis of Structural and Microstructure of Lanthanum Ferrite by Modifying Iron Sand for Microwave Absorber Material Application
Authors: Taufiqu Rochman Nurul , Wisnu Ari Adi
Published: February 2014

Analysis crystal structure of lanthanum ferrite by modifying iron sand has been carried out. Lanthanum ferrite included one of the functional materials which had composition of ABO3 perovskite system. The lanthanum ferrite is prepared by iron sand and lanthanum oxide powders. The mixture was milled for 10h with the various composition of lanthanum content. The samples are sintered at a temperature of 1000 °C for 10h. The microstructure analyses showed that the particle shapes was polygonal with the varied particle sizes and uniform distribution on the surface of the sample. The phase composition of refinement result showed that the lanthanum ferrite formed empirical compound of La0.8Mg0.2Fe0.7Ti0.2Si0.1O3. The La0.8Mg0.2Fe0.7Ti0.2Si0.1O3 phase has a structure orthorombic (P b n m) with lattice parameters a = 5.513(1) Å, b = 5.549(1) Å and c = 7.849(2) Å, α = β = γ = 90°, the unit cell volume of V = 240.2(9) Å3, and the atomic density of ρ = 6.293 gr/cm3. We concluded that this study has been successfully synthesized lanthanum ferrite material from modifying iron sand and has been understood changes in the parameters of the crystal structure and phase composition of this material. It was a great opportunity that the material can be used as a material candidate of absorber electromagnetic waves.
Characterization of Single Phase of La0.8Ba0.2Fe0.3Mn0.35Ti0.35O3 Nanoparticles as Microwave Absorbers
Authors: Manaf Azwar , Wisnu Ari Adi
Published: February 2014

1024x768 Single phase of La0.8Ba0.2Fe0.3Mn0.35Ti0.35O3 nanoparticles were successfully synthesized by mechanical alloying method. The mixture of all precursors were first mechanically milled for 10 hrs and then sintered at a temperature of 1000 °C for 10 hrs in which a fully crystalline material is ensured. The sintered material was then re-milled for 20 hrs to obtain powder-based nanoparticles. The refinement of x-ray diffraction trace for re-milled materials confirmed a single phase material with a monoclinic structure of lattice parameters: a = 5.5182(8) Å, b = 5.5442(8) Å and c = 7.822(1) Å, a = g = 90o and b = 89.63(1)o. The mechanically alloyed and sintered materials in the first mechanical milling resulted in powders with mean size 521 nm. The mean size particle size were reduced further to 62 nm in the second mechanically milled powders. Results of mean crystallite size evaluation for respective powder materials showed almost similar mean crystallite size about 43 nm. In addition, the hysteresis curve showed that the sample is ferromagnetic. Results of VNA evaluation indicated that there were three of absorption peaks with reflection loss values ~ -9.0 dB, ~ -11.5 dB, and ~ -25.0 dB at frequency 9.9 GHz, 12.0 GHz, and 14.1 GHz respectively. The study concluded that the La0.8Ba0.2Fe0.3Mn0.35Ti0.35O3 material with nanoparticles has been successfully synthesized showing a good candidate as microwave absorbing materials. Normal 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;}
Magnetic Properties of Coring Samples from Aceh Basin West Off Sumatera Island
Authors: Gaffar Eddy Z.
Published: February 2014

Three oriented core samples was taken by Japanese MIRAI Research Vessel in Aceh Basin west of the Sumatera Island. 927 small box samples from 3 coring samples was measure. Core bottom ages of three cores are in the last glacial maximum (around 19 kyBP). We measured Natural Remanent Magnetization (NRM), NRM after Alternating Field Demagnetization up to 800 Oe. Measurement of NRM have done by 2G Enterprice Squid, Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization (ARM) on Paleomagnetic Laboratory of Geological Survey of Japan. Result of NRM after Alternating Field Demagnetization shows that there are reverse polarizaty magnetizations. This reverse polarity seems not usual since in Geologic Time Scale 1989 showed that the first reversal polarity was between Brunches Normal Epoch and Jaramillo Epoch beginning at 0.75 Ma There are some possibility of reverse polarity events contained in the three cores mentioned above. The first possibility is the result of the tsunami so that the sediment that settles on the Aceh Basin was a sediment that remain turbid flows that enable magnetic recording on magnetic sediment did not follow directions when he formed so that it seems a polarity reverse polarity when only superficial. The second possibility is indeed occurs under reverse polarity at age 700.000 years. Research in Argentina, South America show that between 11 thousand to two thousand years ago there was an excursion from the magnetic polarity produces some reverse polarity at the time (Nami, 1999). The third possibility was circular variation magnetic.
Sol-Gel Derived ZnO Nanorod Templated TiO2 Nanotube Synthesis for Natural Dye Sensitized Solar Cell
Authors: Kartini Indriana , Evana Evana , Sutarno Sutarno , Chotimah Chotimah
Published: February 2014

Natural dye sensitized solar cells (nDSSC) mostly suffer from low solar cell performance, that vertically aligned nanotube TiO2 as the photoanode is expected to increase the performance by providing higher surface area and direct electron transport. Nanostructured TiO2 films have been fabricated on glass substrates employing ZnO nanorod films as the template. First, vertically oriented ZnO nanorod on a glass substrate was prepared hydrothermally. Then, sol-gel dip-coating technique was used to deposit TiO2. The template films were dip-coated into sols of titanium tetraisopropoxide-ethanol-diethanol ammine with withdrawing rate of 2 cm/min for three- (Ti3) and seven-times (Ti7). After drying at 100 °C for 10 min, the films were calcined at 550 °C for 1h and washed with HCl 3% (v/v). The films were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It is observed that different coating cycles resulted in different film morphologies. Nanotube TiO2 with diameter of ~50 nm was identified for Ti3, while Ti7 displayed sheet-like structure. The diffraction patterns confirmed the presence of only anatase crystalline phase with crystallite size of 10.3 nm (Ti3) and 21.7 nm (Ti7). The dye absorption was red-shifted indicating dye monomeric adsorption on TiO2 via chelation. Enhanced absorption of anthocyanin dye extracted from pericarps of mangosteen (Garcinia mangostana l.) fruit on TiO2 nanotube compared to TiO2 nanoparticle (P25) was observed leading to improved photovoltaic performance of the constructed nDSSC.
The Crystal Structure, Conductivity Character and Ionic Migration of Samarium Doped-Ceria (SDC) and its Composite with Sodium Carbonate
Authors: Rahmawati Fitria , Syarif Dani Gustaman , Paramita Putri Pradnya , Heraldy Eddy
Published: February 2014

This paper discusses the crystal structure, the conductivity character and ionic migration inside Sm0.2Ce0.8O1.9 (SDC) crystal and it’s composite with sodium carbonate salt, Na2CO3 (NSDC). XRD measurement equipped with Le Bail refinement shows that SDC crystallized in single phase of cubic with space group of Fm3m. The addition of Na2CO3 does not change the crystal structure of SDC however it increases the cell parameters. NSDC has a lower ionic conductivity than the SDC at the same temperature. However at 600 °C, SDC provides electronic conductivity which indicates the diffusion of electrons between the electrolyte and electrode caused by the reduction of Ce(IV) to Ce(III). It may cause a short circuit and the fuel cell performance if it is used as electrolyte. Meanwhile, NSDC still produces pure ionic conductivity at 600 °C which indicates a better chemical stability. Based on its capacitance values, it is known that the ionic conductivity of SDC is generated by migration of ions inside grain, while the conductivity of NSDC is generated by the migration of ions between grains or it is named as grain boundaries conductivity.
Synthesis of Tungsten Oxide (WO3) Film on Glass Substrate Using Aqueous Based Solution Spray Deposition Method
Authors: Widiyandari Hendri , Firdaus Iqbal , Purwanto Agus , Slamet V. Gunawan
Published: February 2014

A Tungsten oxide (WO3) film on top of a glass substrate had been successfully constructed. The immobilization of tungsten oxide was performed using spray-deposition method. The precursor volume was varied as 5 mL, 10 mL and 25 mL. Characterization using XRD and SEM yield that precursor volume influence the quality of the film. It was found that the good uniform film was obtained using precursor volume 5 mL and 10 mL. The crack which was resulted from non-uniformity of the film appear when the precursor film was 25 mL.
Preparation of Sulfonate Grafted Silica/Chitosan-Based Proton Exchange Membrane
Authors: Putrie Zarra Miantina , Setyawan Heru
Published: February 2014

Sulfonate-grafted silica/chitosan hybrid (SGSC) membrane has been successfully prepared by in-situ sol-gel method. In this method, grafting of sulfonate onto silica surface was carried out along with membrane formation. Silica sol, with the particle size of about 9 nm obtained from sodium silicate, and amido sulfonic acid were mixed with chitosan solution. The mixture was stirred for 30 minutes and aged at 60 °C for 8 hours. The results showed that sulfonate could be grafted onto the silica surface as indicated by the FTIR spectra. Silica loading is greatly affect the membrane characteristics including water retention, % swelling, and ionic conductivity. Water retention and % swelling decrease with the increase of silica loading. On the other hand, ionic conductivity and acid capacity increase with the increase of silica loading. The increase is related to the amount of silica that carries sulfonate groups. However, there is limitation on the silica loading where membrane cracked if the loading was greater than 1.5 g silica/g chitosan. The ionic conductivity and acid capacity of the membrane can take the values of about 4.2 x 10-6 S/cm and 1.3432 meq/g, respectively.
ZnO-SiO2/Laponite Photocatalyst: Kinetic Study on Photocatalytic Decolorization of Methylene Blue
Authors: Fatimah Is , Yuyun N. Nunani
Published: February 2014

ZnO-SiO2/Laponite was prepared by sol-gel preparation procedure consit of SiO2 pillarization to laponite followed by ZnO dispersion by using zinc acetate as precursor. The obtained material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), diffuse reflectance UV-Visible (DRUV-Vis) and N2 adsorption-desorption analysis. The photocatalytic performance of the amterial in methylene blue decolorization was also investigated. Compared with ZnO-SiO2 nanoparticles, it is concluded that ZnO-SiO2/Laponite possess higher photocatalytic activity which obey Temkin isotherm model.
Coating Steel with Nanosilica by Pulsed Direct Current Electrophoresis for Corrosion Protection
Authors: Putri S. Ni Made Intan , Setyawan Heru
Published: February 2014

The purpose of this paper is to investigate the electrophoretic deposited nanosilica on stainless steel for corrosion protection. The electrophoretic deposition (EPD) was carried out by pulsed direct current (PDC) of silica sol made of sodium silicate. The amplitude and frequency of the PDC were varied in the range of 0.1-0.6 V and 30-80 Hz, respectively. The corrosion protection properties of the silica films were analyzed by Electrochemical Impedance Spectroscopy (EIS) in 2 wt% NaCl solution. The experimental results showed that the silica films exhibit good characteristics as indicated by their high pore resistance and low admittance. The silica film corrosion protection characteristics were influenced by the frequency and amplitude of PDC during preparation of electrophoretic deposition.
Synthesis and Characterization of Solid Polymer Electrolyte from N-Succinyl Chitosan and Lithium Perchlorate
Authors: Fauzi Iqbal , Arcana I. Made , Wahyuningrum Deana
Published: February 2014

Batteries are being developed to solve the global energy crisis. Using portable electronic devices, especially mobile phones and notebook computers, has been increasing, and leading to a strong need of their power-sources. However, secondary batteries using a liquid electrolyte have weaknesses, such as prone to leakage and difficulty of packing. Solid polymer electrolyte is a solution to the existing problems. The objective of this research is to prepare an environmental-friendly and cheap material as the solid polymer electrolyte. In the present study, the effect of succinyl group on to polymer electrolyte membrane which synthesized from chitosan and lithium perchlorate salts was investigated. The N-succinyl chitosan was obtained by reacting chitosan with succinic anhydride. Solid polymer electrolyte membranes were derived from N-succinyl chitosan with different ratios of lithium perchlorate. The degree of deacetylation of chitosan was determined by FTIR analysis. Synthesis of N-succinyl chitosan has been successfully carried out, which is indicated by the characteristic peaks at wavenumbers of 1640 cm-1 and 1560 cm-1 correspond to -C=O stretching and -NH bending of succinyl groups on FTIR spectrum of N-succinyl chitosan. Modification of chitosan by the addition of succinyl group increases the membrane ionic conductivity values. A N-succinyl chitosan membrane contained 10% (w/w) lithium perchlorate showed conductivity of 8.01×10-3 S.cm-1. This solid polymer electrolyte membrane was suggested to have one potential used for polymer electrolyte in lithium battery applications.
Influence of Sintering Temperature on the Translucency of Sintered Zirconia by Cold Isostatic Pressing
Authors: Chin Chuin Hao , Muchtar Andanastuti , Amat Noor Faeizah , Ghazali Mariyam Jameelah , Yahaya Norziha
Published: February 2014

Zirconia-based ceramics exhibit excellent mechanical properties and biocompatibility in dental applications. However, the production of translucent zirconia that offers resemblance to real teeth remains a challenge. This study aims to fabricate zirconia compacts by cold isostatic pressing (CIP) and investigate the influence of sintering temperature on translucency, microstructure, hardness, and density of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Zirconia stabilized with 3 mol% yttria (3Y-TZP) was pressed by uniaxial pressing and later by CIP to produce green bodies in pellet form. Subsequently, the green bodies were sintered at different temperatures (1100 °C to 1300 °C). The specimens were then investigated in terms of translucency, density, and hardness. X-ray diffraction was also performed and the microstructure of the specimens was observed under a scanning electron microscope (SEM). Density and light transmittance tests results showed that zirconia sintered at 1200 °C exhibits the highest density (5.957 g/cm3) and light transmittance intensity. Vickers hardness test showed that higher sintering temperatures result in higher hardness of the sintered zirconia. SEM micrographs illustrate the effect of microstructural changes on the translucency of zirconia. A temperature of 1200 °C is found to be the recommended sintering temperature at which zirconia exhibiting optimum translucency and mechanical properties is produced. CIP is found to be a suitable consolidation method to produce high-density translucent zirconia.
The Phenomenon of Pitting Corrosion Attack on the Milled Aluminium Alloy Al 2618 Plate during Surface Preparation through Sulphuric Acid Anodising
Authors: Subawi Handoko , Sutarno Sutarno
Published: February 2014

This study purposed to investigate corrosion characteristic on aluminium alloy by considering parameters that involved metal preparation, different surface treatment, and alloy types. Through series of the salt spray test, the rolled aluminium sheet revealed higher resistance to surface corrosion rather than milled aluminium plate. However trace elements, as reinforced filler in the metal alloy, may contribute to possible pitting corrosion. By employing sulphuric acid anodising, it revealed higher probability of pitting corrosion to attack the milled aluminium plate surface compared to rolled aluminium sheet. The surface pitting corrosion on the anodised aluminium alloy Al 2618 plate was observed through enlargement of pitting diameter and additional new pitting holes during 500 hours corrosion test. The corrosion propagation grew sharply during 500 hours test and it increased slowly after 750 hours. This study did not evaluate further variables either alloy composition, metal processing, or operation condition in anodising process.
Study of Laser Cladding of Stellite 6 on Nickel Superalloy Substrate with Two Different Energy Inputs
Authors: Kusmoko Alain , Dunne Druce , Li Hui Jun , Nolan David
Published: February 2014

Stellite 6 was deposited by laser cladding on a nickel superalloy substrate (NIS) with energy inputs of 1 kW (NIS 1) and 1.8 kW (NIS 1.8). The chemical compositions and microstructures of these coatings were characterized by atomic absorption spectroscopy, optical microscopy and scanning electron microscopy. The microhardness of the coatings was measured and the wear mechanism of the coatings was examined using a pin-on-plate (reciprocating) wear testing machine. The results showed less cracking and pore development for Stellite 6 coatings applied to the nickel superalloy substrate with the lower heat input (NIS 1). Further, the Stellite coating for NIS 1 was significantly harder than that obtained for NIS 1.8. The wear test results showed that the weight loss for NIS 1 was much lower than for NIS 1.8. It is concluded that the lower hardness of the coating for NIS 1.8, together with the softer underlying substrate structure, markedly reduced the wear resistance of the Stellite 6 coating.
Influence of Oxygen on Microstructures of Ti-Mo-Cr Alloy
Authors: Syarif Junaidi , Kurniawan Eko , Rasani Mohd Rasidi , Sajuri Zainuddin , Omar Mohd Zaidi , Harjanto Sri
Published: February 2014

In this study, the effect of oxygen addition on the microstructures of Ti-18%Mo-10%Cr alloy was investigated. The alloy was fabricated by a powder metallurgy method. The samples were subjected to sintering at 1300°C for 4 hours and furnace cooling. A Bo-Md method was initially applied for predicting stable phase. Calculation using the Bo-Md method showed that Ti-18%Mo-10%Cr alloy have bcc (β) phase at ambient temperature. All samples with various oxygen contents exhibited needle-like structures within equiaxed grains. The increase of oxygen content promoted formation of porosity in the α phase. Calculation of phase stability using JMatProTM showed that the decrease of β phase’s stability was not due to formation of the α phase on sintering, but due to promotion of nucleation and grain growth of diffusional α phase upon furnace cooling. It was also shown that vol.% of porosity of the alloy slightly increased with increasing oxygen content. Therefore, the increase of oxygen concentration could accelerate the formation of α phase and reduce the alloy’s density. The hardness increased as the oxygen concentration increased. The increase of the hardness might be due to combination of the solid solution hardening of oxygen and the precipitation hardening of α phase.
Determination of Band Gap Energy of Semiconductor in Homojunction Structure Devices by Using Customized Microcontroller Based Apparatus
Authors: Triyana Kuwat , Ramadhan Surya , Barata Aji Muhammad Iqbal , Chotimah Chotimah , Harsojo Harsojo
Published: February 2014

We have successfully developed a customized apparatus based on microcontroller for simple band gap energy (Eg) measurement of semiconductors in homojunction structure devices. The apparatus consisted of a data acquisition system based on microcontroller AVR ATMega 128 and a thermos flask equipped with temperature controller. It permits recording of current-voltage (I-V) and temperature and subsequently sends data to a computer to enable the computer processing of such data. For samples under tested, we used two types of commercial diode, i.e. Silicon (1N4007) and Germanium (1N60). In this measurement, the voltage across the resistor was used to calculate the current while the voltage across the diode gave the forward bias voltage. The temperature of diode was varied from 5°C to 80°C. During each I-V measurement, the temperature of diode was maintained to be constant by employing a proportional-integral-derivative (PID) controller to the heater. Furthermore, by varying the temperature of diode, we could extract the saturation currents under reverse bias across the diode of each I-V measurement. For the two types of diode, it is found that the Eg of silicon is 1.13 ± 0.03 eV, while that of germanium is 0.71 ± 0.03 eV. This result is closed to the Eg value of each diode indicated in the respective datasheet. Therefore, it suggests for applying this apparatus for measuring Eg of semiconductor in most homojunction structure devices.
Simultaneous Calibration for MEMS Gyroscopes of the Rocket IMU
Authors: Wahyudi Wahyudi , Susanto Adhi , Widada Wahyu , Hadi Sasongko P.
Published: February 2014

MEMS (Microelectromechanical System), as an advanced sensor technology, is low power, low cost, and small size. Gyroscope sensor produced with microelectromechanical technology is an angular rate sensor. IMU (Inertial Measurement Unit) sensor for rocket should have a very wide range of measurements. At the beginning of the motion, the rocket accelereation is very high, for which the rocket IMU requires a multisensor with different sensitivity. This paper presents the design of the rocket IMU and its calibration method for all MEMS gyroscopes. Calibration for each sensor is necessary including its varying characteristics. The calibration of the gyroscope sensors use three-axis motion simulator model ST 3176 with resolutions 0.00001 for all axes. Simultaneous calibration was mutually applied which require a short calibration time. The results show that root mean square errors (RMSE) of the calibrated gyroscope for all axes are under 2.5 %. Therefore, that the calibrated gyroscope can be used in the proposed real application.
Comparison between Automatic and Semiautomatic Thresholding Method for Mammographic Density Classification
Authors: Uyun Shofwatul , Hartati Sri , Harjoko Agus , Subanar Subanar , Choridah Lina
Published: February 2014

Mammographic density is a novel independent risk factor of breast cancer that reflects the amount of fibroglandular tissue. Breast Imaging Reporting and Data System (BIRADS) density is one of the mammographic density classification schemes which are most widely used by radiologists. Initially, the method used for assessing mammographic density was subjective and qualitative. Recently however, the measurement of mammographic density is more objective and quantitative. In this paper, we propose an alternative model of breast cancer risk factor assessment based on a quantitative approach of density mammogram. This model consists of pre-processing, breast area counting, fibroglandular tissue area counting that uses maximum entropy and multilevel thresholds, and finally breast density counting to determine the risk factor of breast cancer. The proposed model has been tested on a private database from Oncology Clinic Kotabaru, Yogyakarta, Indonesia consisting of 30 mammograms and has been analyzed by some radiologists using the semiautomatic threshold. The result shows that percentage of mammographic density counted by maximum entropy threshold method has the accuracy, sensitivity and specificity of about 87%, 73% and 91% respectively compared to the semiautomatic thresholding method. On the other hand, the accuracy, sensitivity and specificity resulted from using multilevel threshold is about 93%, 87% and 96% respectively. The obtained results suggest that multilevel threshold is perfectly suited for getting quantitative measurement of mammographic density as one of the strongest risk factors for breast cancer.
Image Processing for Multiple Micro-Radiography Images
Authors: Louk Andreas Christian , Suparta Gede Bayu , Hidayah Nurul
Published: February 2014

An image processing method has been developed for processing multiple images of x-ray micro-radiography. An x-ray micro-radiography image reflects quantum mottle so that its information content may tends to be corrupted. Therefore, a digital processing method has been developed to reduce the effect of quantum mottle as well as reducing the noise level. A set of radiographs are collected then summed. An image subtraction by a background image is carried out prior to the summation process. The signal to noise ratio (SNR) and contrast to noise ratio (CNR) after processing are compared with the SNR and CNR prior to the processing. As a result the final image for small specimen under x-ray micro-radiography inspection is better than original image without processing based on SNR and CNR assessments.
Design and Fabrication of Wear Testing Machine for a Fishing Net-Weaving Machine Component
Authors: Intanon Naphatara , Saikaew Charnnarong , Srisattayakul Parinya
Published: February 2014

A hook is an important fishing net-weaving machine component that is used for making fishing net. During the production of fishing net, nylon fiber is in continuous contact with the hooks by sliding on the inner curve of the hooks that results in wear on the hooks. Weight loss of the hooks as the wear resistance measurement was collected to investigate the surface quality of the hooks. Presently, a wear testing machine for a fishing net-weaving machine component is not available for wear resistance study. Thus this work aimed to design and fabricate a wear testing machine that has a mechanism as similar to the actual working conditions as possible and so can provide accurate testing data. It has been proven that the wear testing machine built as a result of this study gave wear testing results extremely similar to those when testing on the actual fishing net-weaving machine.
High Performance Current-Voltage Characterization System for High Resistance Materials
Authors: Munir Muhammad Miftahul , Supriadani Yundi , Budiman Maman , Khairurrijal Khairurrijal
Published: February 2014

The resistivity measurement finds many applications in semiconductors and insulating materials characterization. Conventional digital multimeter can provide resistance measurement up to about 10-200MΩ. However, in some cases, resistances in gigaohms (GΩs) and higher ranges need to be measured accurately. To measure the resistance of high resistivity materials, a programmable voltage source (-100V to +100V) combined with an electrometer system (100pA 10mA) have been built. The electrometer system and programmable voltage source have been calibrated with a calibrator (Fluke 5100B series) and digital multimeter (Fluke 8808A). Materials resistance up to 10 GΩ can be obtained by measuring the current-voltage (I-V) characteristics. It is found that the I-V curve of the 10 GΩ resistor fits very well the linear function with a high linear regression coefficient R2 of 0.999.
Online Monitoring of Copper Leaching Process Heterogeneity Using Electrical Capacitance Volume Tomography
Authors: Haryono Didied , Nugraha Harisma , Taruno Warsito Purwo , Baidillah Marlin Ramadhan , Sulaiman Rommy Iman , Al Huda Mahfudz
Published: February 2014

In this study, we have performed the monitoring of copper leaching process using electrical capacitance volume tomography (ECVT). The ECVT has been used to measure electrical signals generated from the copper leaching process and reconstruct volumetric image of the signals in real time. This method is based on the fact that permittivity changes with the changes of ions concentration caused by leaching reaction. From the 3D image, we were able to analyze the heterogeneity of leaching reaction. There are two important features of leaching measurement, the online capability of the method and the ability to describe the leaching process heterogeneity. The current methods of leaching process usually have only one of the two important features. ECVT with high speed capability can provide both features. The experiment was carried out for 3 hours at room temperature without stirring, in which, copper foil and 2M H2SO4 were used as leaching object and leaching agent. The ECVT reconstructed image shows the heterogeneity permittivity distributions which shows the heterogeneous nature of leaching process.
Flaw Detection in Welded Metal Using Magnetic Induction Tomography
Authors: Sutisna Dona , Ullum Syahrul , Taruno Warsito Purwo , Iman Al Amin Saichul , Baidillah Marlin Ramadhan , Al Huda Mahfudz , Sulaiman Rommy Iman , Haryono Didied
Published: February 2014

Various defects on welded metal can lead to failure of material, so that it needs some routine examination to maintain the material quality. The development of Magnetic Induction Tomography (MIT) in recent years made MIT a potential method for Non Destructive Test (NDT) to be applied in industries. We perform an MIT inspection technique to detect flaw using 2-coils MIT planar sensor that consist of transmitter and receiver coils which is able to detect flaw based on different electrical conductivity and measured as phase shift. This study involves experiment method with measurement of welded steel in two areas, there are normal and defective welded area which amounts to 72 measurement points that conducted with superposition principle. Then simulation of 2-coils planar sensor using Finite Element Method (FEM) software to obtain magnetic field sensitivity using parameter as in the experiment. Result from this measurement showed that phase value in normal welded area is higher than defective welded area, then those data is processed further on reconstruction step by using specific algorithm to obtain reconstructed image. This image able to show the presence of flaw in welded area which is indicated by red spot, and it has a relatively good correlation when compared with radiographic testing film.
Physical-Mechanical Aspects of Preparing Thermal Insulation Materials on the Basis of Liquid (Water) Glass
Authors: Mészárosová Lenka , Drochytka Rostislav
Published: February 2014

In the Czech Republic, liquid glass is mainly used for painting areas with higher surface temperatures, such as bonding agent of heat-resistant concretes, which require higher chemical resistance; it is also used as additional damp proofing for buildings with damp brickwork. Globally, liquid glass is used with expanded perlite as thermal insulation for higher temperature (maximum application temperature of 650 °C). This paper should outline the possible preparation of such material in our conditions and verify, whether it is possible to achieve the bulk density for such material of up to 200 kg/m3, or the potential application of such material.
Possibilities of Reducing the Apparent Porosity of Silica Bricks for the Coke Batteries
Authors: Nevřivová Lenka , Kotouček Miroslav , Lang Karel
Published: February 2014

Silica is used for lining of the upper parts of glass furnaces and their regenerators and for lining of the lids of arc furnaces and for the coke oven batteries construction. Silica bricks represent 60% of refractory material used for a coke battery construction. Coke ovens are generally the largest oven aggregates, where silica material is used. The whole coke oven battery may reach the length up to 80 m due to the chamber sizes. A single coke oven battery contains up to 50.000 tons of refractories [1]. From the material science point of view, the durability of silica bricks depends on numerous parameters including first of all porosity and mineral composition. Microstructure of silica bricks changes during their application due to the heat load, repeated heating and cooling, and direct contact with the oven atmosphere.
The paper discusses the possibility of reducing the apparent porosity and increasing of bulk density of coke oven silica bricks. It describes the effects of an iron dust, microsilica and influence of the compaction pressure on the coke oven silica microstructure. Functional characteristics of the material prepared according to the new standard recipes are compared with the properties of standard silica products.
Comparison of Impedance Spectra of Concrete Recorded with Utilizing Carbon Transition Paste
Authors: Kusák Ivo , Lunak Miroslav
Published: February 2014

NDT method of impedance spectroscopy was used to characterize concrete slab specimens without and with contact graphite compound coating. Differences in tanδ(f), ImZ(f) and ReZ(f) spectra for dry specimens were observed. Furthermore, based on the predominant loss type, the material quality was characterized. Our measurements confirmed the reproducibility of this method. Furthermore, the influence of the concrete specimen composition on their electric parameters was assessed.
Reactivity of Brick Powder in Lime Mortars
Authors: Navrátilová Eva , Rovnaníková Pavla
Published: February 2014

The article deals with the assessment of three brick powders. Their properties are evaluated on the basis of their pozzolanic activity, specific surface area and amorphous area. The brick powders were used in amounts of 20 and 40% as a substitute for binder in lime mortars. The influence of the powders on the properties of the modified plasters in a hardened state was evaluated via the determination of strength characteristics. It was found that not all brick powders are suitable for use in modified lime mortars.
Corrosion Inhibitors as a Prevention
Authors: Taranza Luboš , Drochytka Rostislav
Published: February 2014

Corrosion of reinforcements is one of the most frequent causes of defects of reinforced concrete structures resulting in significantly shortened service life of constructions. By using of corrosion inhibitors the structure failures can be prevented or already started corrosions slowed down and thus to markedly prolong the service life of constructions.
Chloride Diffusion in Limestone Cement Concrete Exposed to Combined Chloride and Sulfate Solutions at Low Temperature
Authors: Sotiriadis Konstantinos , Tsivilis Sotirios , Petranek Vít
Published: February 2014

The chloride diffusion in limestone cement concrete exposed to combined chloride and sulfate solutions at low temperature was studied. For this purpose, a normal Portland cement and two Portland limestone cements (15% and 35% w/w limestone content) were used for concrete preparation. The specimens were immersed in two combined chloride-sulfate solutions of different sulfate content, and stored at 5°C. The total and free chloride contents, as well as the chloride diffusion coefficients were determined for each concrete composition. The results show that the total chloride content and free to total chloride ratio are increased with time. The sulfate content of the corrosive solutions has not a clear effect on total chloride content and chloride diffusion coefficient. It seems that the lower sulfate content results, in general, in higher free to total chloride ratio values. The use of limestone in cement results in higher chloride concentrations in concrete and free to total chloride ratio values. In general, these phenomena are intensified for higher limestone content.
Comparison of the Values of Compressive Strength and Elasticity Modulus of Concrete of Frozen and Unfrozen Specimens
Authors: Brodňan Miroslav
Published: February 2014

In term of practical applications, it is important to know how to change the modulus of elasticity of concrete, which is in wintertime exposed to low temperatures. The partial results of research are presented and oriented on monitoring the changes of the values of modulus of elasticity in time of frozen and unfrozen concrete specimens.
Basic and Hygric Properties of Concrete Containing Fine Ceramic Powder
Authors: Reiterman Pavel , Holčapek Ondřej , Čáchová Monika , Vogel Filip , Jogl Marcel , Konvalinka Petr
Published: February 2014

The motivation for utilization of active admixtures in concrete lies primarily in a positive effect on properties of hardened concrete with regard to its durability. Fine parts complement the grain size distribution curve, but also due to subsequent hydration arise phases with better resistance to aggressive substances from surrounding environment. Process of pozzolanic reaction is also associated with a reduction in open capillary porosity, causing a gradual reduction of the permeability of concrete. The paper presents an experimental program focused on the monitoring of evolution of basic and hygric properties of concrete with fine ceramic powder addition.