Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 40434

Materials and Metallurgical Engineering

Fashion Designer Selection with the Method of Grey Relational Analysis-Based Intuitionistic Fuzzy Multi-Criteria Decision Making
Personnel selection is a decision-making problem based on the determination of the most suitable individual in line with the determined criteria, as known. Particularly in the labor-intensive sectors, such as apparel, the choice of the right personnel is a crucial issue and plays a key role in continuing the life cycle of companies successfully. In this study, the fashion designer recruitment process is examined for the design departments which is one of the most important organs for the apparel companies. For this purpose, the most suitable designer was chosen for an apparel company operating in Izmir province. In order to fulfill the aim, criteria weights which play an active role in the designer selection are obtained through AHP method, and intuitive fuzzy logic sets are utilized to enable the evaluations of the candidates by the experts according to the criteria. In the light of these data, the final choice was conducted with the method of grey relational analysis.
The Effects of Green Purchasing and Supply Policies on Enterprises' Competitiveness in Clothing Sector
On the one hand, ecological approaches and solutions lead the enterprises to differentiation and provide competitive advantage to them, and on the other hand, they reveal protective perspectives in terms of the environment, society, consumer, and employee. Sustainability, which underlies the environmentally-conscious approaches, is based on the protection of environment, individuals’ existences and future resources while the today’s needs are fulfilled. Therefore, sustainability is achieved by the establishment of green supply chain, whose first ring is green purchasing and supply. As it is known, clothing sector is one the oldest and fundamental sectors of the world. At the same time, this sector constitutes one of the most significant milestones of economic development, especially in terms of developing countries. This situation is also valid for Turkish clothing sector. In this context, clothing sector constitutes one of the most significant cornerstones of Turkey’s economical and social development and growth policies towards exportation. The sector involves significant factors in terms of sustainability and green supply chain due to the used raw materials and auxiliary materials, production processes and working conditions. In this study, green purchasing and supply policies, which constitute one of the significant cornerstones of sustainability, and their effects on enterprises are analyzed. For this purpose, green purchasing and supply processes and strategies of clothing enterprises, which operate in the hinterland of İzmir, and their effects on enterprises’ competitiveness are investigated.
An Investigation of Foam Glass Production from Sheet Glass Waste and SiC Foaming Agent
Foam glass is a remarkable material with having incomparable properties like low weight, rigidity, high thermal insulation capacity and porous structure. In this study, foam glass production was investigated with using glass powder from sheet glass waste and SiC powder as foaming agent. Effects of SiC powders and sintering temperatures on foaming process were examined. It was seen that volume expansions (%), cellular structures and pore diameters of obtained foam glass samples were highly depending on composition ratios and sintering temperature. The study showed that various foam glass samples having with homogenous closed porosity, low weight and low thermal conductivity were achieved by optimizing composition ratios and sintering temperatures.
Grain Growth in Nanocrystalline and Ultra-Fine Grained Materials
Grain growth is an important and consequential phenomenon that generally occurs in the presence of thermal and/or stress/strain fields. Thermally activated grain growth has been extensively studied and similarly, there are numerous experimental and theoretical studies published describing stress-induced grain growth in single-phase materials. However, studies on grain growth during the simultaneous presence of an elevated temperature and an external stress are very limited, and moreover, grain growth phenomena in materials containing second-phase particles and solute segregation at GBs have received limited attention. This lecture reports on a study of grain growth in the presence of second-phase particles and solute/impurity segregation at grain boundaries (GBs) during high-temperature deformation of an ultra-fine grained (UFG) Al alloy synthesized via consolidation of mechanically milled powders. The mechanisms underlying the grain growth were identified as GB migration and grain rotation, which were accompanied by dynamic recovery and geometric dynamic recrystallization, while discontinuous dynamic recrystallization was not operative. A theoretical framework that incorporates the influence of second-phase particles and solute/impurity segregation at GBs on grain growth in presence of both elevated temperature and external stress is formulated and discussed. The effect of second-phase particles and solute/impurity segregation at GBs on GB migration and grain rotation was quantified using the proposed theoretical framework, indicating that both second-phase particles and solutes/impurities segregated GBs reduce the velocities of GB migration and grain rotation as compared to those in commercially pure Al. Our results suggest that grain growth predicted by the proposed theoretical framework is in agreement with experimental results. Hence, the developed theoretical framework can be applied to quantify grain growth in simultaneous presence of external stress, elevated temperature, GB segregation and second-phase particles, or in presence of one or more of the aforementioned factors.
Wettability Behavior of Organic Silane Molecules with Different Alkyl-Chain Length Coated Si Surface
Control of surface wettability is very important in various industrial fields. Thus, contact angle hysteresis which is defined as the difference between advancing and receding water contact angles has been paid attention because the surface having low contact angle hysteresis can control wetting behavior of water droplet. Self-assembled monolayer (SAM) formed using organic silane molecules has been used to control surface wettability, in particular, static contact angles, however, the effect of alkyl-chain length in organic silane molecules on the contact angle hysteresis has not yet clarified. In this study, we aimed to investigate the effect of alkyl-chain length (C1-C18) in organic silane molecules on the contact angle hysteresis. SAMs were formed on Si wafer by thermal CVD method using silane coupling agents having different alkyl-chain length. The static water contact angles increased with an increase in the alkyl-chain length. On the other hand, although the water contact angle hysteresis tended to decrease with an increase in the alkyl-chain length, in case of the alkyl-chain length of more than C16 the contact angle hysteresis increased. This could be due to the decrease in the molecular mobility because of the increase in the molecular packing density in chemisorbed silane molecules.
Heat Treatment on Malaysian Hardwood Timbers: The Effect of Heat Exposure at Different Levels of Temperature on Bending Strength Properties
Heat treatment on timbers is a process of applying heat to modify and equip the timbers with new improvised characteristics. It is environmental friendly compared to the common practice of treating timber by chemical preservatives. Malaysian hardwood timbers; Pauh Kijang and Kapur in green condition were heat treated at 150°C, 170°C, 190°C and 210°C in a specially design electronic furnace in one hour duration. The objectives were to determine the effect of heat treatment on bending strength properties of heat treated Pauh Kijang and Kapur in term of Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) and to examine the significance changes at each temperature levels applied. Untreated samples for each species were used as a control sample. The results indicated that the bending strength properties for both species of timbers were affected by the heat exposure. Both MOE and MOR values for heat treated Pauh Kijang were increased when subjected to the specified temperature levels except at 210°C. The values were dropped compared to the control sample and sample treated at 190°C. Heat treated Kapur shows the same pattern of increment on its MOE and MOR values after exposure to heat at three temperature levels used and the values dropped at 210°C. However, differ to Pauh Kijang, even though there were decrement occurred at 210°C but the value is still higher compared to the control sample. The increments of MOE and MOR values are an indicator that heat treatment had successfully improvised the bending strength properties of these two species of hardwood timber. As the good strength of Malaysian timbers used as structural material is limited in numbers and expensive, heat treating timber with low strength properties is an alternative way to overcome this issue. Heat treatment is an alternative method need to be explored and made available in Malaysia as this country is still practicing chemical preservative treatment on the timbers.
Flexible, Hydrophobic and Mechanical Strong Poly(Vinylidene Fluoride): Carbon Nanotube Composite Films for Strain-Sensing Applications
Carbon nanotube (CNT) – polymer composites have been extensively studied due to their exceptional electrical and mechanical properties. In the present study, poly(vinylidene fluoride) (PVDF) – multi-walled CNT composites were prepared by melt-blending technique using pristine (ufCNT) and a modified dilute nitric acid-treated CNTs (fCNT). Due to this dilute acid-treatment, the fCNTs were found to show significantly improved dispersion and retained their electrical property. The fCNT showed an electrical percolation threshold (PT) of 0.15 wt% in the PVDF matrix as against 0.35 wt% for ufCNT. The composites were made into films of thickness ~0.3 mm by compression-molding and the resulting composite films were subjected to various property evaluations. It was found that the water contact angle (WCA) of the films increased with CNT weight content in composites and the composite film surface became hydrophobic (e.g., WCA ~104° for 4 wt% ufCNT and 111.5° for 0.5 wt% fCNT composites) in nature; while the neat PVDF film showed hydrophilic behavior (WCA ~68°). Significant enhancements in the mechanical properties were observed upon CNT incorporation and there is a progressive increase in the tensile strength and modulus with increase in CNT weight fraction in composites. The composite films were tested for strain-sensing applications. For this, a simple and non-destructive method was developed to demonstrate the strain-sensing properties of the composites films. In this method, the change in electrical resistance was measured using a digital multimeter by applying bending strain by oscillation. It was found that by applying dynamic bending strain, there is a systematic change in resistance and the films showed piezo-resistive behavior. Due to the high flexibility of these composite films, the change in resistance was reversible and found to be marginally affected, when large number of tests were performed using a single specimen. It is interesting to note that the composites with CNT content notwithstanding their type near the percolation threshold (PT) showed better strain-sensing properties as compared to the composites with CNT contents well-above the PT. On account of the excellent combination of the various properties, the composite films offer a great promise as strain-sensors for structural health-monitoring.
Observation of a Phase Transition in Adsorbed Hydrogen at 101 Kelvin
While adsorbent surfaces such as graphite are known to increase the melting temperature of solid H2, this effect is normally rather small, increasing to 20 Kelvin (K) relative to 14 K in the bulk. An as-yet unidentified phase transition has been observed in a system of H2 adsorbed in a porous, locally graphitic, Saran carbon with sub-nanometer sized pores at temperatures (74-101 K) and pressures ( > 76 bar) well above the critical point of bulk H2 using hydrogen adsorption and neutron scattering experiments. Adsorption data shows a discontinuous pressure jump in the kinetics at 76 bar after nearly an hour of equilibration time, which is identified as an exothermic phase transition. This discontinuity is observed in the 87 K isotherm, but not the 77 K isotherm. At higher pressures, the measured isotherms show greater excess adsorption at 87 K than 77 K. Inelastic neutron scattering measurements also show a striking phase transition, with the amount of high angle scattering (corresponding to large momentum transfer/ large effective mass) increasing by up to a factor of 5 in the novel phase. During the course of the neutron scattering experiment, three of these reversible spectral phase transitions were observed to occur in response to only changes in sample temperature. The novel phase was observed by neutron scattering only at high H2 pressure (123 bar and 187 bar) and temperatures between 74-101 K in the sample of interest, but not at low pressure (30 bar), or in a control activated carbon at 186 bar of H2 pressure. Based on several of the more unusual observations, such as the slow equilibration and the presence of both an upper and lower temperature bound, a reasonable hypothesis is that this phase forms only in the presence of a high concentration of ortho-H2 (nuclear spin S=1). The increase in adsorption with temperature, temperatures which cross the lower temperature bound observed by neutron scattering, indicates that this novel phase is denser. Structural characterization data on the adsorbent shows that it may support a commensurate solid phase denser than those known to exist on graphite at much lower temperatures. Whatever this phase is eventually proven to be, these results show that surfaces can have a more striking effect on hydrogen phases than previously thought.
Process Optimisation for Internal Cylindrical Rough Turning of Alloy 625 Weld Overlay
Nickel-based superalloys are generally known to be difficult to cut due to their strength, low thermal conductivity, and high work hardening tendency. Superalloy such as alloy 625 is often used in the oil and gas industry as a surfacing material to provide wear and corrosion resistance to components. The material is typically applied onto a metallic substrate through Weld Overlay Cladding, an arc welding technique. Cladded surfaces are always rugged and carry a tough skin; this implies further difficulties to the machining process. The present work utilised design of experiment to optimise the internal cylindrical rough turning for weld overlay surfaces. An L27 orthogonal array was used to assess the effect of the selected four key process variables: cutting insert, depth of cut, feed rate, and cutting speed. The effect of each variable was evaluated through measuring the surface roughness and the machined internal diameter of the test pieces. The optimal cutting conditions were determined based on productivity and the level of tool wear.
Fabrication of Zeolite Modified Cu Doped ZnO Films and Their Response towards Nitrogen Monoxide
Breath analysis represents a promising non-invasive, fast and cost-effective alternative to well-established diagnostic and monitoring techniques such as blood analysis, endoscopy, ultrasonic and tomographic monitoring. Portable, non-invasive, and low-cost breath analysis devices are becoming increasingly desirable for monitoring different diseases, especially asthma. Beacuse of this, NO gas sensing at low concentrations has attracted progressive attention for clinical analysis in asthma. Recently, nanomaterials based sensors are considered to be a promising clinical and laboratory diagnostic tool, because its large surface–to–volume ratio, controllable structure, easily tailored chemical and physical properties, which bring high sensitivity, fast dynamic processand even the increasing specificity. Among various nanomaterials, semiconducting metal oxides are extensively studied gas-sensing materials and are potential sensing elements for breathanalyzer due to their high sensitivity, simple design, low cost and good stability.The sensitivities of metal oxide semiconductor gas sensors can be enhanced by adding noble metals. Doping contents, distribution, and size of metallic or metal oxide catalysts are key parameters for enhancing gas selectivity as well as sensitivity. By manufacturing doping MOS structures, it is possible to develop more efficient sensor sensing layers. Zeolites are perhaps the most widely employed group of silicon-based nanoporous solids. Their well-defined pores of sub nanometric size have earned them the name of molecular sieves, meaning that operation in the size exclusion regime is possible by selecting, among over 170 structures available, the zeolite whose pores allow the pass of the desired molecule, while keeping larger molecules outside.In fact it is selective adsorption, rather than molecular sieving, the mechanism that explains most of the successful gas separations achieved with zeolite membranes. In view of their molecular sieving and selective adsorption properties, it is not surprising that zeolites have found use in a number of works dealing with gas sensing devices. In this study, the Cu doped ZnO nanostructure film was produced by SILAR method and investigated the NO gas sensing properties. To obtain the selectivity of the sample, the gases including CO,NH3,H2 and CH4 were detected to compare with NO. The maximum response is obtained at 85 C for 20 ppb NO gas. The sensor shows high response to NO gas. However, acceptable responses are calculated for CO and NH3 gases. Therefore, there are no responses obtain for H2 and CH4 gases. Enhanced to selectivity, Cu doped ZnO nanostructure film was coated with zeolite A thin film. It is found that the sample possess an acceptable response towards NO hardly respond to CO, NH3, H2 and CH4 at room temperature. This difference in the response can be expressed in terms of differences in the molecular structure, the dipole moment, strength of the electrostatic interaction and the dielectric constant. The as-synthesized thin film is considered to be one of the extremely promising candidate materials in electronic nose applications. This work is supported by The Scientific and Technological Research Council of Turkey (TUBİTAK) under Project No, 115M658 and Gazi University Scientific Research Fund under project no 05/2016-21.
Sintering Properties of Mechanically Alloyed Ti-5Al2.5Fe
In this study, Ti5Al2.5Fe alloy was prepared by powder metallurgy. The elemental titanium, aluminum, and iron powders were mechanically alloyed for 10 h in a vacuum atmosphere. A stainless steel jar and stainless steel balls were used for mechanical alloying. The alloyed powders were then sintered by hot vacuum pressing at 950°C for a soaking time of 30 minutes. Pure titanium was also sintered at the same conditions for comparison of mechanical properties and microstructural behavior. The samples were investigated by scanning electron microscopy, XRD analysis, and optical microscopy. Results showed that after mechanical alloying a homogeneous distribution of the elements was obtained and desired α-β structure was determined. Ti-5Al-2.5Fe alloy was successfully produced, and the alloy showed enhanced mechanical properties compared to commercially pure titanium.
Microwave Dielectric Properties and Microstructures of Nd(Ti₀.₅W₀.₅)O₄ Ceramics for Application in Wireless Gas Sensors
Carbon monoxide is a substance produced by the incomplete combustion. It is toxic even at concentrations of less than 100ppm. Since it is colorless and odorless, it is difficult to detect. CO sensors have been developed using a variety of physical mechanisms, including semiconductor oxides, solid electrolytes, and organic semiconductors. Many works have focused on using semiconducting sensors composed of sensitive layers such as ZnO, TiO₂, and NiO with high sensitivity for gases. However, these sensors working at high temperatures increased their power consumption. On the other hand, the dielectric resonator (DR) is attractive for gas detection due to its large surface area and sensitivity for external environments. Materials that are to be employed in sensing devices must have a high-quality factor. Numerous researches into the fergusonite-type structure and related ceramic systems have explored. Extensive research into RENbO₄ ceramics has explored their potential application in resonators, filters, and antennas in modern communication systems, which are operated at microwave frequencies. Nd(Ti₀.₅W₀.₅)O₄ ceramics were synthesized herein using the conventional mixed-oxide method. The Nd(Ti₀.₅W₀.₅)O₄ ceramics were prepared using the conventional solid-state method. Dielectric constants (εᵣ) of 15.4-19.4 and quality factor (Q×f) of 3,600-11,100 GHz were obtained at sintering temperatures in the range 1425-1525°C for 4 h. The dielectric properties of the Nd(Ti₀.₅W₀.₅)O₄ ceramics at microwave frequencies were found to vary with the sintering temperature. For a further understanding of these microwave dielectric properties, they were analyzed by densification, X-ray diffraction (XRD), and by making microstructural observations.
Influence of Build Orientation on Machinability of Selective Laser Melted Titanium Alloy-Ti-6Al-4V
Selective laser melting (SLM), a promising additive manufacturing technology (AM) has huge potential in the fabrication of Ti-6Al-4V near-net shape components. However, the poor surface finish of the components fabricated from this technology requires machining to achieve desired accuracy and tolerances. Therefore, a systematic understanding of machinability of SLM fabricated Ti-6Al-4V components is paramount to improve the productivity and product quality. Considering the significance of machining in SLM fabricated Ti-6Al-4V components, this research is aimed to study the influence of build orientation on machinability characteristics by performing slow speed orthogonal cutting tests. In addition, the machinability of SLM fabricated Ti-6Al-4V is compared with conventionally produced wrought Ti-6Al-4V to understand the influence of SLM technology on machining. It was found that build orientation influenced cutting forces, chip formation, and surface integrity during orthogonal cutting of SLM Ti-6Al-4V samples. In addition, a difference in machinability of SLM Ti-6Al-4V and wrought Ti-6Al-4V was observed. Also, results obtained from the slow speed orthogonal cutting tests are similar to the results obtained from turning tests, highlighting the practical importance of microstructure and build orientation on machinability of SLM Ti-6Al-4V.
Adsorption and Desorption Behavior of Ionic and Nonionic Surfactants on Polymer Surfaces
Experimental and computational studies are combined to elucidate the adsorption proprieties of ionic and nonionic surfactants on hydrophobic polymer surface such us poly(styrene). To present these two types of surfactants, sodium dodecyl sulfate and poly(ethylene glycol)-block-poly(ethylene), commonly utilized in emulsion polymerization, are chosen. By applying quartz crystal microbalance with dissipation monitoring it is found that, at low surfactant concentrations, it is easier to desorb (as measured by rate) ionic surfactants than nonionic surfactants. From molecular dynamics simulations, the effective, attractive force of these nonionic surfactants to the surface increases with the decrease of their concentration, whereas, the ionic surfactant exhibits mildly the opposite trend. The contrasting behavior of ionic and nonionic surfactants critically relies on two observations obtained from the simulations. The first is that there is a large degree of interweavement between head and tails groups in the adsorbed layer formed by the nonionic surfactant (PEO/PE systems). The second is that water molecules penetrate this layer. In the disordered layer, these nonionic surfactants generate at the surface, only oxygens of the head groups present at the interface with the water phase or oxygens next to the penetrating waters can form hydrogen bonds. Oxygens inside this layer lose this favorable energy, with a magnitude that increases with the surfactants density at the interface. This reduced stability of the surfactants diminishes their driving force for adsorption. All that is shown to be in accordance with experimental results on the dynamics of surfactants desorption. Ionic surfactants assemble into an ordered structure and the attraction to the surface was even slightly augmented at higher surfactant concentration, in agreement with the experimentally determined adsorption isotherm. The reason these two types of surfactants behave differently is because the ionic surfactant has a small head group that is strongly hydrophilic, whereas the head groups of the nonionic surfactants are large and only weakly attracted to water.
Processing Maps for Hot Deformation to Develop New Thermomechanical Processing Routes to Achieve Ultrafine Grained Microalloyed Steel
The use of low carbon micro-alloyed steels has been expanded in many strategic applications such as ship building, automobile industry, line pipe, building construction, bridges, storage tanks, pressure vessels etc. Demand of improvement of the existing strength is increased day by day to enhance the performance of the components. Continual strategy is there to reduce the cost of raw materials and production without compromising of product quality. Thus, new scientific approach should be explored to optimize the processing parameters to achieve ultrahigh strength steels. In the present study, hot working behaviour of low C microalloyed steel has been studied by physical simulation on thermo-mechanical simulator (Gleeble 3800). The hot deformation study was conducted in the temperature range 700-1100°C after austenitization at 1200°C for 60s. The strain rates used in the study was in the range 0.001 to 10s-1 for a total true strain of 0.7. Processing windows were determined using dynamic materials model in order to determine the safe hot working domains and these are correlated with the microstructural evolution. Detailed microstructural evolution has been investigated using optical microscopy, SEM and EBSD. Finally, multi-pass deformation schedules have been designed in safe workable region to produce defect free ultrafine grained microstructure through the mechanisms of strain induce ferrite transformation and dyanamic recrystallization. Accordingly, hot rolling of the microalloyed steel achieved attractive mechanical properties due to the formation of ultrafine microstructure (av. grain size ~300 nm) without any high strain deformation. Therefore, the thermo-mechanical controlled rolling schedule in accordance with the designed schedule can be extremely useful to develop ultrahigh strength steel for industrial application.
Cr³⁺/SiO₄⁴⁻ Codoped Hydroxyapatite Nanorods: Fabrication and Microstructure Analysis
In this study, nanorods of Cr³⁺/SiO₄⁴⁻ codoped hydroxyapatite (Cr³⁺/SiO₄⁴⁻-HA) were synthesized successfully and rapidly through microwave irradiation technique, using (Ca(NO₃)₂•4H₂O), ((NH₄)₂HPO₄), (SiC₈H₂₀O₄) and (Cr(NO₃)₃.9H₂O) as source materials for Ca²⁺, PO₄³⁻, SiO₄⁴⁻ and Cr³⁺ ions, respectively. The impact of dopants on the phase formation and microstructure of the powders were investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectrum analysis (FT-IR) and Field emission electron microscopy (FESEM) techniques. XRD analysis showed that with an incorporation of Cr³⁺/SiO₄⁴⁻ ions into HA structure resulted in peak broadening and reduced peak height due to the amorphous nature and reduced crystallinity of the resulting HA powder. FTIR spectroscopy revealed the existence of the different vibrational modes matching to phosphates and hydroxyl groups. The FESEM analysis showed a change in the crystal shape from spherical to rod shaped particles upon Cr³⁺ doping into the crystal structure.
Photoluminescence and Energy Transfer Studies of Dy3+ Ions Doped Lithium Lead Alumino Borate Glasses for W-LED and Laser Applications
Lithium Lead Alumino Borate (LiPbAlB) glasses doped with different Dy3+ ions concentration were synthesized to investigate their viability in solid state lighting (SSL) technology by melt quenching techniques. From the absorption spectra, bonding parameters (ð) were investigated to study the nature of bonding between Dy3+ ions and its surrounding ligands. Judd-Ofelt (J-O) intensity parameters (Ω = 2, 4, 6), estimated from the experimental oscillator strengths (fex) of the absorption spectral features were used to evaluate the radiative parameters of different transition levels. From the decay curves, experimental lifetime (τex) were measured and coupled with the radiative lifetime to evaluate the quantum efficiency of the as-prepared glasses. As Dy3+ ions concentration increases, decay profile changes from exponential to non-exponential through energy transfer mechanism (ETM) in turn decreasing experimental lifetime. In order to investigate the nature of ETM, non-exponential decay curves were fitted to Inkuti–Hirayama (I-H) model which further confirms dipole-dipole interaction. Among all the emission transition, 4F9/2  6H15/2 transition (483 nm) is best suitable for lasing potentialities. By exciting titled glasses in n-UV to blue regions, CIE chromaticity coordinates and Correlated Color Temperature (CCT) were calculated to understand their capability in cool white light generation. From the evaluated radiative parameters, CIE co-ordinates, quantum efficiency and confocal images it was observed that glass B (0.5 mol%) is a potential candidate for developing w-LEDs and lasers.
Effect of Al2O3 Nanoparticles on Corrosion Behavior of Aluminum Alloy (Al-4.5wt%Cu-1.5wt%Mg) Fabricated by Powder Metallurgy
In this research the effect of Al2O3 nanoparticles on corrosion behavior of aluminum base alloy(Al-4.5wt%Cu-1.5wt%Mg) has been investigated. Nanocomopsites reinforced with variable contents of 1,3 & 5wt% of Al2O3 nanoparticles were fabricated using powder metallurgy. All samples were prepared from the base alloy powders under the best powder metallurgy processing conditions of 6 hr of mixing time , 450 MPa of compaction pressure and 560°C of sintering temperature. Density and micro hardness measurements, and electrochemical corrosion tests are performed for all prepared samples in 3.5wt%NaCl solution at room temperature using potentiostate instrument. It has been found that density and micro hardness of the nanocomposite increase with increasing of wt% Al2O3 nanoparticles to Al matrix. It was found from Tafel extrapolation method that corrosion rates of the nanocomposites reinforced with alumina nanoparticles were lower than that of base alloy. From results of corrosion test by potentiodynamic cyclic polarization method, it was found the pitting corrosion resistance improves with adding of Al2O3 nanoparticles . It was noticed that the pits disappear and the hysteresis loop disappears also from anodic polarization curve.
Spark Plasma Sintered Single Phase Ca-α-SiAlON Ceramic Utilizing Nano-Sized Precursors at Lower Temperatures
The present work aimed to the development of nitrogen rich single phase alpha(α)-SiAlON by spark plasma sintering (SPS) technique, utilizing nanosized starting powders and incorporating calcium oxide (CaO) as a densification additive. A decrease in sintering temperature along with enhancement of mechanical properties was anticipated. Spark plasma sintering was used to process single phase Ca-α-SiAlON employing nanosized precursors at relatively lower temperatures of 1500 °C and 1600 °C for three different holding times (10, 20 & 30 min) at respective sintering temperatures. The chemical composition of nitrogen rich Ca-α-SiAlON was fixed to be Ca0.8Si9.2Al2.8O1.2N14.8 for all the samples, corresponding to m and n values of 1.6 and 1.4 respectively in the general formula of Ca-α-SiAlON. The densification and mechanical properties of the sintered ceramics were examined to investigate the effect of sintering temperature and holding time on the properties. All samples were completely densified at each set of processing parameters. For either sintering temperatures (at all holding times), a remarkable amalgamation of properties, namely hardness and toughness, was obtained for all the samples; and the greatest values for both the properties were attained at 30 min holding time, with Vickers hardness values of 21.6 GPa and 20.5 GPa and fracture toughness values of 7.3 MPa√m and 9.7 MPa√m for sintering temperatures of 1500 °C and 1600 °C, respectively. In order to inspect the variation in mechanical properties, the phases formed during sintering process were identified and correlated to the changes in mechanical properties of the samples. Microstructural analysis of cross-section and fracture surface was carried out for samples sintered at 1500 °C and 1600 °C at 30 min holding time. The relative lower hardness (20.5 GPa) for sample sintered at 1600 °C and 30 min holding time was associated to the larger grain size as compared to sample sintered at 1500 °C and 30 min holding time. With regard to fracture toughness, sintering at either 1500 °C or 1600 °C for 30 min holding time, the yielded fracture toughness values were consequence of formation of elongated α-SiAlON grains.
Structural and Electromagnetic Properties of CoFe2O4-ZrO2 Nanocomosites
The nanocomposites of CoFe2O4-xZrO2 with different loadings of ZrO2 (x = 0.025, 0.05, 0.075, 0.1 and 1.5) were prepared using ball mill method. All the samples were prepared at 980°C/1h using microwave sintering method. The x-ray diffraction patterns show the existence of tetragonal/monoclinic phase of ZrO2 and cubic phase of CoFe2O4. The effects of ZrO2 on structural and microstructural properties of CoFe2O4 composite ceramics were investigated. It is observed that the density of the composite decreases and porosity increases with x. The magnetic properties such as saturation magnetization (Ms), and Coercive field were calculated at room temperature. The Ms is decreased with x while coercive field is increased with x. The dielectric parameters exhibit the relaxation behavior in high-frequency region and showing increasing trend with ZrO2 concentration, showing suitable
Environmental Effect on the Flexural and Surface Roughness Properties of Halloysite Nanotube-Reinforced Polyester Composites
The environmental degradation of the flexural and surface roughness properties of halloysite nanotube-reinforced polyester composites has been investigated with special focus on the effects of water-methanol exposure for 24 h. The influence of water-methanol uptake on flexural and surface roughness properties of composites was evaluated. Flexural modulus and flexural strength were slightly decreased while the flexural strain increased because of liquid absorption. Significant increase in surface roughness was observed as also confirmed by scanning electron microscopy (SEM) images.
Flotation Recovery of Gold-Loaded Fine Activated Carbon Using Emulsified Diesel and Kerosene as Collectors
The recovery of fine activated carbon with adsorbed gold in the cyanidation tailings of a small-scale gold plant was investigated due to the high amount of gold present. In the study, collectors that were used are kerosene and diesel. Emulsification of the oils was done to improve its collecting property, thus also the recovery. It was found out that the best hydrophile lypophile balance (HLB) of emulsified diesel and kerosene oil is 13 and 12 respectively. The amount of surfactants (SPAN 20 and TWEEN 20) for the best stability of the emulsified oils was found to be 10% in both kerosene and diesel. Optical microscopy showed that the oil dispersion in the water forms spherical droplets like features. The higher the stability, the smaller the droplets and their number were increasing. The smaller droplets indicate better dispersion of oil in the water. Consequently, it will have a greater chance of oil and activated carbon particle interaction during flotation. Due to the interaction of dispersed oil phase with carbon, the hydrophobicity of the carbon will be improved and will be attached to the bubble. Thus, flotation recovery will be increased. Results showed that the recovery of the fine activated carbon using emulsified diesel or kerosene is three times more effective than using pure diesel or kerosene.
Rapid Assessment of Processing Variability for Comminution Circuit Design
With the recent commercialisation of advanced routine drill core imaging systems, a large volume of drill core images can now be collected rapidly on a routine basis at high resolution. Mineral maps of the imaged drill core samples can also be generated more easily, which allows for the ore texture to be more readily available and easier to be quantified at drill core scale. This paper introduces a new method for rapid assessment of the variability in the orebody on the comminution circuit behaviour from drill core scan images. In this method, mineralogically classified drill core images are subjected to texture analysis and classification to produce different texture classes. Each of the texture classes is expected to exhibit unique comminution behaviour. Texture classes are correlated with a small number of comminution parameters obtained from a few physical tests. This correlation allows for a rapid prediction of the comminution parameters of the drill holes without the need to perform an extensive test work campaign. A case study in which this method was applied to predict the comminution parameters from six drill holes of an iron-oxide copper-gold deposit, is presented. The predicted comminution parameters feed JKSimMet simulations to evaluate the variability of the comminution circuit throughput. The results offered a snapshot of the throughput variability of the examined area with a reduced amount of time and physical tests required. Compared to the laborious manual logging procedures that currently form the industry standard, this new method that utilises automated drill core scan images can potentially increase the efficiency of building deposit scale geometallurgical models and improve flowsheet design.
Determining the Electrospinning Parameters of Poly(ε-Caprolactone)
Electrospinning is a versatile way to occur fibers at nano-scale and polycaprolactone is a biomedical material which has a wide usage in cartilage defects and tissue regeneration. PCL is biocompatible and durable material which can be used in bio-implants. Therefore, electrospinning process was chosen as a fabrication method to get PCL fibers in an effective way because of its significant adjustments. In this research study, electrospinning parameters was evaluated during the producing of polymer tissue scaffolds. Polycaprolactone’s molecular weight was 80.000 Da and was employed as a tissue material in the electrospinning process. PCL was decomposed in dimethylformamid(DMF) and chloroform(CF) with the weight ratio of 1:1. Different compositions (1%, 3%, 5%, 10% and 20 %) of PCL was prepared in the laboratory conditions. All solvents with different percentages of PCL have been taken into the syringe and loaded into the electrospinning system. In electrospinning dozens of trial were applied to get homogeneously uniform scaffold samples. Taylor cone which is crucial point for electrospinning characteristic was occurred and changed in different voltages up to the material compositions’ conductivity. While the PCL percentages were increasing in the electrospinning, structure started to arise with droplets, which was an expressive problem for tissue scaffold. The vertical and horizontal layouts were applied to produce non-woven structures at all.
Investigation on the Properties of Particulate Reinforced AA2014 Metal Matrix Composite Materials Produced by Vacuum Infiltration Method
Particulate reinforced aluminum matrix composites have gained more importance in automotive, aeronautical and defense industries due to their specific properties like as low density, high strength and stiffness, good fatigue strength, dimensional stability at high temperature and acceptable tribologic properties. In this study, 2014 Aluminium alloy used as a matrix material and B4C and SiC were selected as reinforcements components. For production of composites materials, vacuum infiltration method was used. In the experimental studies, the reinforcement volume ratios were defined by mixing as totally 10% B4C and SiC. Aging treatment (T6) was applied to the specimens. The effect of T6 treatment on hardness was determined by using Brinell hardness test method. The effects of the aging treatment on microstructure and chemical structure were analysed by making XRD, SEM and EDS analysis on the specimens.
Reducing the Chemical Activity of Ceramic Casting Molds for Producing Decorated Glass Moulds
Ceramic molding can produce castings with fine detail, smooth surface and high degree of dimensional accuracy. All these features are the key factors for producing decorated glass moulds. In the ceramic mold casting process, the fundamental parameters affecting the mold-metal reactions are the composition and the properties of the refractory materials used in the production of ceramic mold. As a result of the reactions taking place between the liquid metal and mold surface, it is not possible to achieve a perfect surface quality, a fine surface detail and maintain a high standard dimensional tolerances. The present research examines the effects of the binder composition on the structural and physical properties of the zircon ceramic mold. In the experiment, the ceramic slurry was prepared by mixing the refractory powders (zircon(ZrSiO4), mullit(3Al2O32SiO2) and alumina (Al2O3)) with the low alkaline silica (ethyl silicate (C8H20O4Si)) and acidic type gelling material suitable binder and gelling agent. This was followed by pouring that ceramic slurry on to a silicon pattern. After being gelled, the mold was removed from the silicon pattern and dried. Then, the ceramic mold was subjected to the reaction sintering at 1600°C for 2 hours in the furnace. The stainless steel (SS) was cast into the sintered ceramic mold. At the end of this process it was observed that the surface quality of decorated glass mold.
Lithium-Ion Battery State of Charge Estimation Using One State Hysteresis Model with Nonlinear Estimation Strategies
Battery state of charge (SOC) estimation is an important parameter as it measures the total amount of electrical energy stored at a current time. The SOC percentage acts as a fuel gauge if it is compared with a conventional vehicle. Estimating the SOC is, therefore, essential for monitoring the amount of useful life remaining in the battery system. This paper looks at the implementation of three nonlinear estimation strategies for Li-Ion battery SOC estimation. One of the most common behavioral battery models is the one state hysteresis (OSH) model. The extended Kalman filter (EKF), the smooth variable structure filter (SVSF), and the time-varying smoothing boundary layer SVSF are applied on this model, and the results are compared.
Experimental Study on the Preparation of Pelletizing of the Panzhihua's Fine Ilmenite Concentrate
This paper focuses on the preparation of pelletizing with the Panzhihua ilmenite concentrate to satisfy the requirement of smelting titania slag. The effects of the moisture content, mixing time of raw materials, pressure of pellet, roller rotating speed of roller, drying temperature and time on the pelletizing yield and compressive strength were investigated. The experimental results show that the moister content was controlled at 2.0% ~ 2.5%, mixing time at 20 min, the pressure of the ball forming machine at 13 ~ 15 mpa, the pelletizing yield can reach up 85%. When the roller rotating speed is 6 ~ 8 r/min while the drying temperature and time respectively is 350 °C and 40 ~ 60 min, the compressive strength of pelletizing is more than 1500 N. The preparation of pelletizing can meet the requirement of smelting titania slag.
Design Modification of Lap Joint of Fiber Metal Carbon Reinforced Aluminium Laminates
The continuous development and exploitation of materials and designs have diverted the attention of the world towards the use of robust composite materials known as fiber-metal laminates in many high-performance applications. The hybrid structure of fiber metal laminates makes them a material of choice for various applications such as aircraft skin panels, fuselage floorings, door panels and other load bearing applications. The synergistic effect of properties of metals and fibers reinforced laminates are responsible for their high damage tolerance as the metal element provides better fatigue and impact properties, while high stiffness and better corrosion properties are inherited from the fiber reinforced matrix systems. They are mostly used as a layered structure in different joint configurations such as lap and but joints. The FML layers are usually bonded with each other using either mechanical fasteners or adhesive bonds. This research work is also focused on modification of an adhesive bonded joint as a single lap joint of carbon fibers based CARALL FML has been modified to increase interlaminar shear strength and avoid delamination. For this purpose different joint modification techniques such as the introduction of spews and shoulder to modify the bond shape and use of nanofillers such as carbon nano-tubes as a reinforcement in the adhesive materials, have been utilized to improve shear strength of lap joint of the adhesively bonded FML layers. Both the simulation and experimental results showed that lap joint with spews and shoulders configuration have better properties due to stress distribution over a large area at the corner of the joint. The introduction of carbon nanotubes has also shown a positive effect on shear stress and joint strength as they act as reinforcement in the adhesive bond material.
Olive Stone Valorization to Its Application on the Ceramic Industry
Olive oil is a product of particular importance within the Mediterranean and Spanish agricultural food system, and more specifically in Andalusia, owing to be the world's main production area. Olive oil processing generates olive stones which are dried and cleaned to remove pulp and olive stones fines to produce biofuel characterized to have high energy efficiency in combustion processes. Olive stones fines fraction is not too much appreciate as biofuel so it is important the study of alternative solutions to be valorized. The main objective of this study is to investigate the effects of olive stones addition on the properties of fired clay bricks for building construction. Olive stones were substituted by volume (7.5%, 15% and 25%) to brick raw material in three different sizes (lower than 1 mm, lower than 2 mm and between 1 and 2 mm). In order to obtain comparable results, a series without olive stones was also prepared. The prepared mixtures were compacted in laboratory type extrusion under a pressure of 2.5MPa for rectangular shaped (30 mm x 60 mm x 10 mm). Dried and fired industrial conditions were applied to obtain laboratory brick samples. Loss on ignition, linear shrinkage, bulk density, porosity, water absorption and compressive strength of fired samples were investigated and compared with a sample manufactured without biomass. Results obtained have showed that olive stone addition decreased mechanical properties due to the increase in water absorption, although values tested satisfied the requirements in EN 772-1 about methods of test for masonry units (Part 1: Determination of compressive strength). Finally, important advantages related with the properties of bricks as well as their environmental effects could be obtained with the use of biomass studied to produce ceramic bricks. The increasing of the percentage of olive stones incorporated decreased bulk density and then increased porosity of bricks. On the one hand, this lower density supposes a weight reduction of bricks to be transported, handled as well as the lightening of building; on the other hand, biomass in clay contributes to autothermal combustion which involves lower fuel consumption during firing step. Consequently, the production of porous clay bricks using olive stones could reduce atmospherical emissions and improve their life cycle assessment, producing eco-friendly clay bricks.