Abstract: The corrosion behavior of electroless Ni coated SiC particle reinforced squeeze cast aluminum
based composite was investigated by potentiodynamic scanning (PDS) and electrochemical impedance
spectroscopy (EIS) techniques in aerated and deaerated chloride solutions. Microstructural and interfacial
characterization of the composite was carried out by using an optical microscope, scanning electron
microscope (SEM), energy dispersion spectroscopy (EDS) and X-ray diffractometer (XRD). It has been
observed that electroless Ni coating of SiC particles is not an effective method to improve its corrosion
resistance in structural applications containing halide solution.
Abstract: In this study, mechanically alloyed Al-12Si/TiB2/h-BN composite powder was deposited onto aluminum substrates by atmospheric plasma spraying. Wear performance of the coating was investigated with respect to the structural evolution of the composite powder coating. Non-lubricated ball-on-disk tests were used to examine the wear resistance of the coatings. The worn surfaces were examined using scanning electron microscopy and energy dispersive spectroscopy to elucidate the wear mechanisms operating at the sliding interface. It has been observed that TiB2 and in situ formed AlN and Al2O3 phases in combination with h-BN solid lubricant strongly affect the wear performance of the coating.
Notes: This article is an invited paper selected from presentations at the 2009 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Expanding Thermal Spray Performance to New Markets and Applications: Proceedings of the 2009 International Thermal Spray Conference, Las Vegas, Nevada, USA, May 4-7, 2009, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2009.
Abstract: In this study, mechanically alloyed Al–12Si / SiO2 composite powder was deposited onto an aluminum substrate by atmospheric plasma spraying. The composite coating consisting of in-situ formed Al2O3 reinforced hypereutectic Al–18Si matrix alloy was achieved. The produced coatings were extensively analyzed with respect to X-ray diffraction (XRD). The XRD patterns of the coatings include Al, Si and Al2O3 phase formation. Mechanical properties of layers were examined by Dynamic Ultra-micro hardness test machine for estimating Young’s modulus due to load-unload sensing analysis. The hardness and Young’s modulus of the composite coatings sprayed at different plasma current and the distance were measured under 200, 400, 600, 800 and 1000mN of applied peak loads by indentation technique. The effects of spray distance and arc current on the hardness and Young’s modulus have been investigated. Additionally, it was observed that the arc current and spray distance strongly influence the mechanical properties of the coatings.
Abstract: Polyacrylonitrile (PAN)-based carbon nanofiber supported Fe/Co/Ni ternary alloy nanoparticles were prepared by using the electrospinning technique for potential fuel cell applications. The solution was prepared by adding pre-solved catalytic precursor into PAN/DMF solution. The effect of PAN and catalyst precursor concentration on solution properties (viscosity and conductivity) and heat stabilization temperature has been investigated. Electrospun nanofibers were characterized by field emission scanning electron microscope, transmission electron microscope, energy dispersive spectrometer and X-ray diffractometer. It has been found that ternary nanoparticle size is in the range of 5–115 nm (average: 20 nm) and is a crystal alloy of Fe, Co and Ni. Also, TEM results demonstrate that in some regions metal nanoparticles tend to agglomerate into larger particles mainly due to the non-uniform distribution of nanoparticles in as-spun condition. PAN-derived carbon nanofiber mean diameter was measured as 200 nm by varying from 40 nm to 420 nm.
Abstract: An important issue for atmospheric plasma sprayed metal coatings is the oxidation involved during processing that significantly affects its phase composition and microstructure and thus the overall coating properties. In this study, suspension thermal spraying was used to manufacture cast iron coatings with high amounts of graphite carbon as solid-lubricant, because graphite structure is considerably diminished in molten droplets of the spray material due to the dissolution into molten iron and/or the oxidation. Additional graphite formation based on the soot reaction of liquid hydrocarbon was observed. Oxidation strongly affects the soot reaction during suspension thermal spraying. Therefore, setting-up of a shroud around the plasma plume is quite effective to prevent the oxidation of hydrocarbon.
Notes: This article is an invited paper selected from presentations at the 2009 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Expanding Thermal Spray Performance to New Markets and Applications: Proceedings of the 2009 International Thermal Spray Conference, Las Vegas, Nevada, USA, May 4-7, 2009, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2009.
Abstract: In the present study, mechanically alloyed Al–12Si, B2O3 and TiO2 powder was deposited onto
an aluminum substrate using atmospheric plasma spraying (APS). The effects of mechanical
alloying (MA) time and plasma parameters (arc current and primary/secondary/carrier gas flow
rate) on in-situ reaction intensity and in-flight particle characteristics (temperature and velocity)
have been investigated. It has been observed that MA time has a remarkable effect on powder
morphology and relative amount of in-situ formed TiB2 and γ-Al2O3. In-flight particle diagnostic
measurements demonstrate that among the plasma parameters arc current has the strongest effect
on in-flight particle velocity and temperature. Also, results indicate that in-flight particle velocity
is more dominant than temperature on the relative amount of in-situ formed phases.
Abstract: In this study, the corrosion susceptibility of aluminum matrix composites reinforced with artificially oxidized SiO2 and sol–gel Fe/TiO2 coated silicon carbide particles (SiCp) has been investigated. Corrosion behavior of the composites, fabricated by the liquid metal infiltration technique, was established in chloride containing alkaline environments by cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS) techniques. It has been found that, sol–gel coating of SiC particles with Fe/TiO2 has a detrimental effect on the corrosion characteristics of A380–SiC metal matrix composite.
Abstract: In the present work, mechanically alloyed Al-12Si and SiO2 powder was deposited onto an aluminium substrate by atmospheric plasma spraying (APS) to obtain a composite coating consisting of in-situ formed alumina reinforced hypereutectic Al-18Si matrix alloy. The effects of spray parameters and in-flight particle characteristics on reaction intensity between selective powders were investigated. Obtained results are tested by artificial neural network (ANN) techniques. An ANN model is built, trained and tested. Multilayer perception model has been constructed with back propagation algorithm using the input parameters of arc current, spray distance, in-flight particle velocity and temperature. The ANN model was found able to predict the coating hardness, substrate temperature, alumina intensity and silicon intensity in the range of input parameters considered. This study demonstrates that ANN is very efficient for predicting output parameters of experimental studies.
Abstract: Aluminum nitride layers on aluminum are formed by the barrel nitriding in nitrogen gas, and duplex coatings are performed with the plasma nitriding in nitrogen and argon gas after the barrel nitriding. Aluminum nitride films with high thickness, high surface hardness, and good adhesion can be obtained on aluminum surfaces by using the above process. Hardness and Young's modulus of the AlN formed by the barrel nitriding is estimated by means of the rules of mixture. The microstructure of the AlN is proved to be composed of Al and AlN. It is suggested that the AlN formed by the barrel nitriding can play a role as the adhesion improvement of the AlN formed by the plasma nitriding. Furthermore, a microindentation test, which can obtain indentation load-penetration displacement curves, is performed in order to investigate the film fracture of the AlN.
Abstract: In the present study, mechanically alloyed Al–12Si/TiB2/h-BN composite powder was deposited onto an aluminum substrate by atmospheric plasma spraying. The effect of mechanical alloying (MA) and plasma spray parameters on composite powder and coating structure were investigated. It has been observed that the MA process has a significant effect on the composite powder morphology and reactivity between the selective powders. Results also demonstrate that, at relatively high milling time h-BN decomposes into B and N and forms a solid solution. Also, it has been found that, the relative amount of the in-situ formed AlN through the reaction between h-BN and Al and/or the decomposition of Al–B–N solid solution is independent from the plasma parameters (arc current and secondary gas flow rate). However, spray parameters remarkably affects the coating hardness due to coarsening of Si during the solidification of the coating.
Abstract: Oxidation behavior of in-flight particle in plasma spray process significantly affects the coating properties and performance. Therefore, understanding the relationship between in-flight particle characteristics and oxidation phenomena is essential to improve the coating properties. This paper presents the oxidation behavior of in-flight aluminum particles and its relationship between in-flight particle temperature and velocity. Aluminum powder was injected into the plasma flame at different spray conditions and collected at different stand-off distances by using a specially designed equipment. It has been observed that in-flight particle velocity is the main parameter that affects the oxidation of aluminum particles.
Abstract: In this study, a new nitriding technique is suggested to produce aluminum nitride film with high adhesion on aluminum substrate. Bilayer aluminum nitride can be produced on aluminum substrate using barrel nitriding and plasma nitriding. Furthermore, plasma nitriding parameters are also investigated. It is suggested that the aluminum nitride film thickness strongly depends on the gas mixture ratio and the treatment time, and the surface morphology of the film has close relation to the gas pressure.
Abstract: Graphite degradation in plasma sprayed cast iron coatings is a technological barrier for achieving superior wear resistant coatings. Therefore, there is a need to understand the in-flight particle behavior of cast iron powder. In this study, methane (CH4) and methane/carbon dioxide (CO2) mixture has been introduced into the plasma flame to decrease the in-flight particle temperature of cast iron powder in order to prevent the oxidation and dissolution of graphite as well as provide additional free carbon. It has been observed that, CH4 and CH4/CO2 addition remarkably decreases the in-flight particle temperature as a result of the in-situ endothermic reactions. Also, results demonstrate that while CH4 and CH4/CO2 addition does not alter the microstructure, it slightly increases the graphite content in cast iron coatings.
Abstract: In this study, a new nitriding process is proposed to produce the aluminum nitride on the aluminum surface. A process of combined barrel and plasma nitriding techniques was used. By using the barrel nitriding process, an aluminum nitride layer with high thickness can be formed within a matter of hours, and the surface hardness can be improved by using the plasma nitriding. It is suggested that a combined technique of the barrel nitriding and the plasma nitriding is one of the most promising surface treatments for the aluminum.
Abstract: Electrospinning process was utilized to fabricate Ag doped TiO2 ultrafine nanofibers. The produced
nanofibers were characterized by using scanning electron microscopy (SEM), X-ray diffraction
(XRD) and differential thermal analysis (DTA). The effect of process parameters such as electic field,
concentration of solution, flow rate has been investigated. In addition, photocatalysis properties of nanofibers
were measured by UV/Vis spectrophotometer. With addition of Ag, photocatalytic properties
of the nanofibers have been increased. It was determined that Ag doping to TiO2 was improved photocatalytic
properties and thus increased antibacterial activity as photocatalytic filters.
Abstract: In the present study, the wear behavior of in situ formed Al2O3 reinforced hypereutectic Al–18Si matrix composite coatings have been investigated. These coatings were successfully fabricated with mechanically alloyed Al–12Si and SiO2 powder deposited on aluminum substrates by atmospheric plasma spraying (APS). The produced samples were characterized by means of microscopic examinations, hardness measurements and wear tests. The obtained results pointed out that the amount of in situ formed Al2O3 particles increased with increasing spray distance and decreasing in-flight particle velocity and temperature, which was accompanied by an improvement in hardness and wear resistance.
Abstract: Graphite formation and degradation in thermally sprayed cast iron coatings is a technological barrier for achieving superior wear resistant coatings. Therefore, there is a need to understand the in-flight particle behavior of cast iron powder and introduce new approaches to control the graphite content. In this study, it has been demonstrated that the graphite content can be controlled by means of in-flight particle diagnostic. For this purpose, cast iron coatings were plasma sprayed under a variety of spray conditions and characterized by using an optical microscope, X-ray diffractometer and electron probe micro-analyzer. As a result, a significant amount of graphite with respect to a wide range of in-flight particle temperature and velocity was preserved in cast iron coatings.
Abstract: TiO2 nanofibers with a diameter of 54–78 nm have been successfully prepared by electrospinning method using a solution that contained poly(vinyl pyrrolidone) (PVP) and Ti(IV)-isopropoxide. The effect of viscosity and applied electric field on the morphology of the electrospun titania fibers was investigated. It has been observed that the increase in electric field causes bead formation and discontinuity in nanofiber morphology.
Abstract: In this study, the wetting behavior of oxide and metallic coated SiC substrate with Al—Si—Mg alloy has been investigated. SiC substrate and particles were coated with SiO2, TiO2, and metallic Ni by using thermo-chemical treatment, sol-gel and electroless coating techniques, respectively. Also, the effect of doping elements (Ni, Cu and Fe in TiO2 coating) on the wettability has been investigated. Coatings were characterized by SEM, EDS, XRD, and by means of surface roughness. Contact angle results demonstrate that metallic Ni coating significantly improves the wettability. However, doping elements did not alter the results due to their detrimental effect on surface roughness.
Abstract: In the present study, mechanically alloyed Al–12Si and SiO2 powder was deposited onto an aluminum substrate by atmospheric plasma spraying (APS) to obtain a hypereutectic Al-Si based in-situ alumina formed composite coating. The effect of process parameters (arc current, spray distance, nozzle type, oxygen gas support and substrate cooling) on in-flight particle characteristics (temperature and velocity) and in-situ alumina formation were investigated. It has been observed that while arc current and nozzle inner diameter strongly affects the in-flight particle characteristics and in-situ alumina formation, the effect of oxygen gas support is insignificant. Also, the results show that the substrate cooling considerably hinders alumina formation.
Abstract: An investigation was carried out on the production of electroless Ni coated 20vol% SiC particle reinforced composite by squeeze casting. The morphology of the coating, microstructural, interfacial, and mechanical properties of the composite were characterized by using an optical microscope, image analyzer, scanning electron microscope (SEM), energy dispersion spectrometer (EDS), and X-ray diffractometer (XRD). The evaluation of microstructure shows that the matrix phase exhibits a pore-free and dentritic structure, and particle segregation. Interfacial examinations indicate that electroless nickel coating has not degraded during the fabrication process and prevent the formation of Al4C3.
Abstract: In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al–12Si and SiO2 powder was deposited onto an aluminum substrate by atmospheric plasma spraying (APS) to obtain a composite coating consisting of in-situ formed alumina reinforced hypereutectic Al–18Si matrix alloy. The effects of spray parameters (arc current and spray distance) and in-flight particle characteristics (temperature and velocity) on in-situ reaction intensity (alumina and silicon) have been investigated. The results show that, in-situ alumina formation and silicon intensity strongly depend on in-flight particle characteristics, spray distance and substrate temperature.
Abstract: In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al–12Si, B2O3 and TiO2 powder was deposited onto an aluminum substrate using atmospheric plasma spraying (APS). It has been observed that, during the coating process, TiB2 and Al2O3 are in-situ formed through the reaction between starting powders and finely dispersed in hypereutectic Al–Si matrix alloy. Also, obtained results demonstrate that in-situ reaction intensity strongly depends on spray conditions.
Abstract: The corrosion mechanisms of the clusters and gas porosities in Al-Si-Mg
based metal matrix composites(MMCs) reinforced with SiC particles were
determined by SEM observations in deaerated 3.5 wt.% NaCl aqueous
solutions. It was found that the composites shown severe pitting behaviors
which could be due to the presence of aggressive Cl ions in the
solution. In addition, SEM observations revealed that corrosion preferentially
started around of cluster and gas porosities and these observations
were correlated with the dissolution mechanisms of aluminium.
Abstract: An investigation was carried out on SnO2 coating of SiC particles by sol-gel technique and the production of SnO2 coated 20 vol% SiC particle reinforced composite and unreinforced matrix alloy by squeeze casting. The morphology of the coating and microstructural, interfacial and mechanical properties of the composite were characterized by using an optical microscope, image analyzer, scanning electron microscope (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD). It has been found that the coating is not degraded during the fabrication process; in other words, SnO 2 coating by sol-gel technique is an effective way to improve the matrix/reinforcement interfacial properties.
Abstract: In this study, the effect of SiC particle volume fraction on the corrosion behavior of Al-Si-Mg based SiCp reinforced metal matrix composites in both aerated and deaerated 3.5 wt.% NaCl aqueous solutions has been investigated. Composites reinforced with 10 and 20 vol.% SiC particles were produced by compocasting technique and then extruded. The corrosion susceptibility was analyzed by measuring the cyclic potentiodynamic polarization. The corrosion rates of the samples were determined by using E-pit, E-corr and i(corr) values obtained from polarization curves. The surface morphology of the composites was determined by an optical microscopy and scanning electron microscopy (SEM). In addition, X-ray diffraction (XRD) technique has been used in order to determine the phases occurring at the matrix/SiC interface. The obtained results indicate that the corrosion resistance of the composites decreased with increased SiC particle content.
Abstract: The wettability of ceramic reinforcements by liquid aluminum plays an important role on the composite properties. Unfortunately, the wettabiliy of covalent bonded SiC ceramic reinforcements by aluminum alloy is generally poor. In this study, methods to promote wettability, the effect of different ceramic coatings on the wettability of SiC reinforcements by liquid aluminum and the effect of coating on the interface and composite properties have been investigated.
Abstract: The influence of age hardening on the corrosion behavior of Al-Si-Mg-based metal matrix composites (MMCs) has been investigated in aerated and deaerated 3.5 wt% aqueous NaCl solutions. Silicon carbide particle (SiCp) reinforced composites consisting of 10 and 20 vol% SiC(p)s are produced by the compocasting technique. After the extrusion process, the composites are artificially aged (T6). The corrosion resistances of the aged composites are analyzed by measuring the cyclic potentiodynamic polarization. The surface morphology of the composites before and after the corrosion tests are determined by using metallographic methods and scanning electron microscopy (SEM). In addition, the X-ray diffraction technique (XRD) has been used to determine the phases that occur at the matrix-reinforcement interface. The results demonstrate that the E-pit values of unreinforced matrix alloy and composites increase negatively with increasing aging time. It is also observed that corrosion preferentially starts at the interface of Al-Mg2Si and Al-SiCp.
Abstract: TiO2 (anatase) and TiO2/PVP nanocomposite nanofibers with average diameters of 53 and 109 nm, respectively, were synthesized via sol-gel chemistry in combination with an electrospinning process. This produced continuous nanotibers that were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). TiO2 nanotibers were obtained through thermal oxidation of TiO2/PVP in air and the weight loss was determined by thermal gravimetric analysis (TGA). Mechanical properties were studied with a nanoscale three-point bending test. Elastic properties of single nanofibers are reported as measured by atomic force microscopy (AFM) three-point bending on a mesoporous membrane as support. The mean of elastic moduli for TiO2 and TiO2/PVP nanofibers were found to be 75.6 and 0.9 GPa, respectively. (c) 2005 Elsevier B.V. All rights reserved.
Abstract: In this study, an investigation was carried out in order to determine the effect of annealing temperature on the mechanical properties of H13 steel. Heat treatments were applied on samples at different temperatures in both, the as-received and as-quenched conditions. In order to indicate the effect of heat treatment temperature, hardness measurements and tensile tests were performed at all chosen temperatures. At relatively high temperatures the mechanical properties of the H13 steel have been diminished considerably.
Abstract: This paper describes the friction and wear behaviour of Cr2O3/Ni8.5Cr7Al5Mo2Si2I32FcTiO(2) coatings for bearing materials. These coatings were successfully deposited on low carbon steels using a flame spray technique. The produced samples were characterized by means of an optical microscope and microhardness tester. The microstructural observations showed that the layers contain some inhomogeneities such as porosity, crack-like defects, unmelted particles, oxides and inclusions. The structures with the inhomogeneities strongly influence their wear/friction properties. The friction and wear experiments were performed under dry and acid environments using a pin-on-plate configuration against AISI 303 counter material for different loads. It was found that in acid environment, the amount of wear loss is less than that of in dry condition and applied load level is more effective in dry condition.
Abstract: In this study, low carbon steel substrate was coated with WC-Ni powder by using plasma spray process in order to increase the wear and corrosion resistance of the material. Wear tests were applied to the produced samples under different wear conditions. The coatings were characterized with regard to microstructure and mechanical properties. The microstructure of the coating was determined using an optical microscope, image analyzer and X-ray diffraction methods. It has been observed that WC-Ni coating has a high wear resistance especially in acid condition.
Abstract: In this study, an in vitro wear behaviour of dental ceramic porcelain veneers was investigated. The ceramic veneers were fabricated on NiCrMo substrate through glazing method. Surface morphology of the veneers was characterized by scanning electron microscopy (SEM). The wear tests were conducted with the porcelain veneers at different loads under in vitro conditions through a pin-on-plate configuration against a human tooth counterbody. The worn surfaces of the porcelain veneers and human tooth counter material were examined by optical microscope. Porcelain veneer samples exhibit higher wear resistance and lower dynamic friction coefficient and wear rate do not change significantly at a given distance up to 100 N of applied load.
Abstract: Recently, ceramic porcelains, plasters, wastes and metalic substrates have been widely used as tooth prosthesis laboratory materials. Patients, who applied to dental physician, wanted that their aestetic apperances and chewing functions well fix because of the renewing of being broken or decreased teeth by several reasons. The tooth porcelains have been used as tooth renewing materials. The main ceramic raw material of the tooth porcelains consists of clay, kaolen, quarz and feldspat. In this study, synthesis method, properties and importance of the materials using at dental medicine were investigated.
Abstract: The High Velocity Oxy-Fuel (HVOF) thermal spraying process can be used to produce dense hard coatings onto metallic surfaces with a good bond between the coating and Substrate. These coatings have been applied in many different industries to provide wear, erosion and corrosion protection. In this study, the NiCr coatings were deposited on the stainless steel substrates by HVOF technique. Microstructural characterization of the coatings was examined by using optical microscope. Corrosive wear behaviour of these coatings was evaluated through a pin-on-plate configuration, the wear tests were carried out at ambient temperature in 1% H2SO4 solutions. It has been found that NiCr coating is more resistance against to wear in acid condition rather than air condition.
Abstract: Plasma spray technique was used to deposit SiC-AlSi composite coatings, having approximate thickness of 400 mum, of commercially available AlSi alloy powders fabricated thereby mixing with SiC particles. The coating microstructure was investigated by a combination of optical microscopy, SEM, EDX and XRD. The coatings had layered morphologies because of deposition and solidification of successive melted or semimelted particles. SiC particles were randomly distributed in AN layers. The coatings were subjected to dry sliding wear against hardened steel counterbodies using pin-on-disc type apparatus and microhardness measurement was carried out through a standard microhardness tester. It has been found that these coatings possess porosities, and the hardness values and wear behaviour of the coatings strongly depend on porosity, oxidized, unmelted and semimelted particles.
Abstract: Ni-graphite coatings, due to their high hardness and chemical inertness, are often used as protective coatings against friction and corrosion. In this paper, the preparation of a nickel-graphite coating on mild steel substrates using plasma spraying technique and the properties of the coatings are presented. The microstructural characterization of the coatings was examined by optical microscope and image analyzer. Hardness and elastic modulus measurements were applied to the fabricated coatings through a dynamic ultra-microhardness machine. Also, phase analysis of the coatings was determined by XRD techniques. It has been found that, samples produced by plasma spray technique possess oxide, unmelted and semimelted particles, inclusions and porosity.
Abstract: Molybdenum was deposited on cast-iron substrates using an air plasma spray system. The coated samples were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction, image analyzing, and microhardness. The Mo coatings possess porosity, unmelted particles, oxides, and inclusions. It was also found that the microhardness of Mo coatings decreased from the edge of the coating to cast-iron substrate.
Abstract: The principle aim of this paper is to investigate effects on performance of protective multilayer coatings with Cr2O3/Mo/cast iron architecture in order to use in an internal combustion engines. With this regard, Cr2O3 powders were deposited on Mo coated cast iron substrates using an atmospheric plasma spray system. The coated samples were characterized by means of an optical microscope, image analyzer (LUCIA), scanning electron microscope (SEM) and X-ray diffraction. Mechanical properties of the multilayers were determined by using standard and dynamic ultra microhardness machines. Wear tests were conducted with the Cr2O3/Mo and Mo coated cast iron substrates at 89 N under dry sliding conditions through a pin-on-plate arrangement against AISI 303L steel counterbody. The microstructural analysis of worn surfaces were examined by SEM. Thermal behavior of the Cr2O3/Mo coatings was scrutinized using a thermal cyclic machine without external load. The microstructural observations showed that the multilayers contain some inhomogeneities such as porosity, crack-like defects, unmelted particles, oxides and inclusions. The structures with the inhomogeneities strongly influenced their mechanical, wear/friction and thermal properties. It was also found that Cr2O3 layer significantly increased the performance of Mo coated cast iron substrate as a protective layer. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: The effect of porosity on the mechanical and fracture behaviour in Al-Si matrix alloy and composites reinforced with SiC particles of 10 and 20 vol.% in the as-cast state and after extrusion process has been studied. Matrix alloy and composites were fabricated by compocasting and extrusion. Samples were characterized by optical microscopy, image analyzer, scanning electron microscopy and tensile tests. The results demonstrate that hot extrusion considerably reduces the porosity, while size and distribution of the reinforcement particles are also affected. In the point of fracture behaviour, the existence of large porosity is more effective. (C) 2003 Elsevier B.V. All rights reserved.
Abstract: The recrytallization behaviour of Al-Si-Mg matrix composites reinforced with SiC particles of 10 and 20 vol.% and unreinforced matrix alloy have been studied. Also, the effect of annealing temperature and time on grain growth and particle coarsening has been evaluated. Cast ingots of the matrix alloy and composites were extruded at 500degreesC at an extrusion ratio of 10:1. The microstructures and hardness of the composite samples have been investigated. It has been found that particle volume fraction and size affect the recrystallization temperature of the materials.
Abstract: Functionally gradient coatings are coating systems, which are used to increase performances of high temperature components in the hot gas turbine section of gas turbine engines, diesel engines, in aerospace and aircraft applications. These coatings consist of a transition from the metallic bond layer to cermet and from cermet to the ceramic layer. Functionally gradient materials were applied on stainless steel substrates via an atmospheric plasma spray technique. The coating architecture was NiCrAl, 75% NiCrAl + 25% MgZrO3, 50% NiCrAl + 50% MgZrO3, 25% NiCrAl + 75% MgZrO3 and 100% MgZrO3 layers, respectively. The FGM samples were thermally cycled at temperature range of 47 and 600degreesC for periods of 303 s and then characterised by optical microscopy, image analyser, SEM and XRD. Microhardness of the layers was measured using a standard microhardness tester. The obtained results are presented. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: Metal substrate components have been coated with functionally gradient coatings (FGCs) to improve thermal barrier properties and heat efficiency of high temperature materials in gas turbine engines, nuclear fusion equipment, diesel engines, jet engines and space shuttles. In this study, functionally graded materials (FGMs), which contain NiCrAl, 75% NiCrAl + 25% MgZrO3, 50% NiCrAl + 50% MgZrO3, 25% NiCrAl + 75% MgZrO3 and 100% MgZrO3 coating layers, have been produced onto stainless steel substrates via an atmospheric plasma-spray technique. The fabricated samples were characterized by means of an optical microscope, scanning electron microscope (SEM), X-ray diffraction and microhardness tester. The wear behaviour of the FGCs was evaluated under dry conditions using a pin-on-plate configuration. The surface morphologies of the FGM samples after wear experiments were examined by SEM. The wear mechanism of the FGCs is discussed based on SEM observation of the worn surface morphologies. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: In this study, Mo coatings were fabricated on cast-iron substrate using a plasma-spray technique for diesel engine motors. In order to undergo cyclic heating because of piston element in combustion chamber, thermal behaviour of these coatings were scrutinized through a thermal cycling machine. These Mo coatings were tested at temperature range of 47-600degreesC for periods of 303 s under thermal cycling conditions. The effects of thermal cycling on the properties of the samples were characterized by using an optical microscope, image analyzer, SEM, X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and microhardness tester. Microstructural observations showed that the coatings possessed lamellae structure with boundaries. XRD, TGA and DSC results revealed that Mo coatings transformed to Moo and MoO3 during the thermal cycling process. It was found that an increase in porosity and residual thermal stresses after thermal cycling influenced the hardness results of the samples considerably. It was also observed to be a delimination between coating and substrate after thermal cycling. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: This paper demonstrates the successful application of NiCr coatings on stainless steel substrates using a high velocity oxy-fuel technique for corrosion applications. We present preliminary results of fabrication and microstructural characterization of NiCr coatings. These coatings were characterized by means of an optical microscope, image analyzer, scanning electron microscope and X-ray diffraction (XRD). A microhardness tester was used in order to determine the mechanical properties of the coating. Microstructural observations pointed out that the NiCr layers possessed porosity, oxidized, unmelted and semimelted particles, and inclusions. XRD results indicated that the outstanding phase of NiCr powder and coating was Ni. It was also found that the microhardness values decreased from the coating to substrate. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: In order to protect machining parts against wear and corrosion in automotive, aerospace, pulp and paper industries, they are coated with Mo-based materials. For these specific applications, Mo coatings were fabricated on cast-iron substrates using an atmospheric plasma-spray system and their friction and wear behavior were evaluated. The Mo coatings were subjected to sliding wear against AISI 303 counter bodies under dry and acid environments. A pin-on-plate type of apparatus was used with normal loads of 49, 89 and 129 N, and sliding speed of 1 Hz. In the steady state, it was demonstrated that the Mo-coated samples under dry conditions had slightly higher wear resistance than under acid conditions tested under a load of 129 N. Several wear failure mechanisms, such as local plastic deformation, cracks, pits, debris, grooves, scratches and tracks, were identified after the tests. (C) 2003 Elsevier Science B.V. All rights reserved.
Abstract: An investigation was carried out to determine the effect of Si and Mg on ageing behavior of Al-7%Si-0.7%Mg matrix composites reinforced with SiC particles of 10 and 20 vol.% and unreinforced matrix alloy. The samples were produced by compocasting technique and extruded. The produced samples were characterized by optical microscope, image analyzer, scanning electron microscope and X-ray mapping. The obtained results were compared with the previous study, which was studied on Al-5%Si-0.2%Mg matrix alloy and composites. It has been found that, the formation of some reaction products, mechanical properties and age hardening behavior of the composites strongly depend on Si and Mg content of the matrix alloy. In addition, increasing the Mg and Si content from 0.2 and 5 wt.% to 0.7 and 7wt.% respectively, increase the critical temperature and hardening efficiency values.
Abstract: Nanofiber media with its unique properties like large specific surface area, small pore size, and high porosity meet industry’s demand for finer filtration and higher throughput. Nanospider™ technology allows us to produce high quality of nanofibers at industrial scale for a wide range of filtration applications. The flexibility of this technology enables to produce a wide range of polymers on different kind of substrates with high web and nanofiber uniformity. The effect of basis weight, mean nanofiber diameter, morphology and relative nanofiber length on filtration efficiency and pressure drop has been well investigated and discussed in detail.
Abstract: Nanofiber media with its unique properties like low basis weight, small fiber diameter, small pore size, high specific surface area meet industry’s demand for finer filtration and higher throughput. Nanospider™ technology, which is a free liquid surface electrospinning process, allows producing high quality of nanofibers at industrial scale for a wide range of filtration applications. The nanofiber media produced by Nanospider™ technology exhibits high web and fiber uniformity. Nanofiber coating provides remarkable increases in filtration efficiency at relatively small increases in pressure drop. Nanofiber filter media also demonstrates improved filter life and more dust holding capacity.
Abstract: Nanofibers unique architecture provides an almost linear path as the electron carrier. Losses in the material while travelling are significantly lowered, resulting in higher conversion efficiency. Additionally, nanofibers can harvest more photons (thus making more electrons) because they are more accessible for the light when compared to nanoparticles. Nanofibers embedded in the DSSC module can make up to 25% more energy than conventional DSSC modules with nanoparticles.
Abstract: Nanofibers have drawn significant attention in many fields including high-performance filter media, composites, textiles, catalysts, electronic and optical devices, drug delivery system, and tissue engineering. Nanofiber technology is one of the fastest growing areas in the material science and engineering fields.
Among the various methods of producing nanofibers, electrospinning attracts much interest mainly due to being a simple and cost-effective method. In recent years, we witnessed the potential growth in the numbers of patents and publications related with this technology.
In this presentation, Nanospiderâ„¢ technology will be introduced which allows nanofibers to be produced on an industrial scale for a number of applications. Nanospiderâ„¢ is a free liquid surface electrospinning process. In other words, there are no nozzles, needles or spinnerets in the equipment which significantly reduces the mechanical complexity of the equipment, therefore allowing longer running times and greater cost efficiency. Free liquid surface electro-spinning allows nature to optimize the distance between Taylor cones, rather than setting the distance arbitrarily. This allows for industrial scale production rates, consistent web morphology and fiber homogeneity.
Abstract: Reactive plasma spraying (RPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. However, the coating quality strongly depends on spray parameters therefore on-line measurement of in-flight particle characteristics can provide a unique tool for optimizing the coating properties and process conditions. In the present study, mechanically alloyed Al–Si and SiO2 powder was deposited onto an aluminum substrate by using atmospheric plasma spraying (APS). The effect of spray parameters on in-situ reactions and in-flight particle characteristics were investigated. The results showed that, alumina is formed through the in-situ reaction between aluminum and silica. Also, it has been observed that particle characteristics strongly depend on spray parameters therefore monitoring particle behavior is essential for optimizing spray parameters in reactive plasma spraying.
Abstract: In-situ plasma spraying (IPS) is a promising process to fabricate composite coatings with in-situ formed thermodynamically stable phases. In the present study, mechanically alloyed Al–12Si and SiO2 powder was deposited onto an aluminum substrate by atmospheric plasma spraying (APS) to obtain a composite coating consist of in-situ formed alumina reinforced hypereutectic Al-18Si matrix alloy. The effect of gun current of plasma spraying on the corrosion behavior of the composite coating has been investigated. The corrosion resistances of the composite coatings were analyzed by measuring the cyclic potentiodynamic polarization technique. The surface morphology of composite coatings before and after corrosion tests were determined by using metallographic methods and scanning electron microscopy (SEM). Obtained results are discussed in detail.
Abstract: The process of electrospinning was utilized to fabricate Ag doped TiO2 ultrafine nanofibers. The
Produced nanofibers were characterized by using scanning electron microscopy (SEM), X-Ray
diffraction (XRD) and DTA/TG. The effect of process parameters such as electic field, concentration
of solution, flow rate has been investigated. In addition, photocatalysis properties of nanofibers were
measured by photoactivity experiments. With addition of Ag, photocatalytic properties of the
nanofibers have been increased. As a result, the increase in antimicrobial properties reported in
literature and fabricates even better photocatalytic filters.
Abstract: The corrosion behaviors of T8 tempered Al─Si─Mg/SiCp metal matrix composites (MMCs) were investigated in aerated and deaerated 3.5wt% NaCl solutions by potentiodynamic polarization technique in this study. In order to determine the effect of cold work on the electrochemical behavior, the composites were cold-worked to a plastic strain of 4, 6, 10, 25 and 50%. A major change in the corrosion morphologies were observed cold working ratio increased from 4 to 50%. For example, electrochemical analysis indicated that the corrosion current densities (icor) of 20% vol. SiC composite increased from 0.8 to 5.9 with increasing cold-worked ratio after T8 temper. In addition, we find that there is a significant coloration between corrosion susceptibility and level of cold work.
Abstract: Günümüzde teknolojinin ilerlemesine paralel olarak malzemelerden istenen özellikler de değişmektedir. Metal matrisli kompozitler diğer malzemelere göre daha düşük maliyete ve daha fazla rijitliğe sahiptirler. Döküm yöntemiyle de üretilebilen bu kompozitler, üretim aşamasında ortaya çıkan yüksek porozite miktarları nedeniyle kullanımları sınırlanmaktadır. Literatürde bu porozitelerin tipleri ve kompozitin mekanik özellikleri üzerine etkileri ile ilgili bir çok çalışma mevcuttur ancak bu etkilerin korozyon açısından incelenmesi yok denecek kadar azdır. Al/SiC kompozitlerde porozite, SiC parçacıkların matris alaşımına katılması sırasında belli bölgelerde topaklanması, Al/SiC arayüzeyindeki adhezyon eksikliği, ergimiş matrise difüze olan gazlar veya üretim sonrası uygulanan ısıl işlemler sonucunda meydana gelen hacim daralmaları nedeniyle oluşabilir. Sonuçta, porozitelerin oluştuğu bölgelerde kompozitin elektrokimyasal aktiviteleri değişir ve korozyon karakteristikleri farklılaşmaya başlar. Bu çalışmada karıştırmalı döküm ve ekstrüzyon yöntemleri ile üretilen Al-Si-Mg matrisli kompozitlerde görülen porozite tiplerinin korozyon karakteristiği üzerine etkisi incelenmiştir.
Abstract: The production and potential applications of metal matrix composites have been dramatically increased with technological developments since 20 years. Compared to metallic alloys, ceramic particulate reinforced metal matrix composites (MMCs) own improved mechanical properties. One of the most widespread ceramic-metal combinations for MMCs is SiC/Al system. Although extensive investigations have been carried out on the mechanical properties of aluminum-based metal matrix composites (AMMCs), the corrosion behavior of these composites are still incomplete. This problem is one of the main drawbacks to the widespread use of MMCs in engineering applications. In this study, the corrosion behaviour of AMMCs was investigated.
Abstract: Bu çalışmada, %10 ve %20 hacim oranlarında SiC partikül katkılı A356 matrisli kompozitlerin ve katkısız matris alaşımının yaşlanma davranışları üzerine soğuk deformasyonun etkisi araştırılmıştır. Döküm yoluyla üretilen numuneler ekstrüzyon işlemine tabi tutulduktan sonra 150oC ve 175oC'de yaşlandırılmışım Deformasyon oranının yaşlanma davranışına etkisini incelemek amacıyla numuneler sırayla %2, 4, 6, 10, 25 ve 50 oranlarında soğuk deformasyona tabi tutularak 175oC'de yaşlandırılmışım Soğuk deformasyon görmüş numunelerin yaşlandırma işlemi sonrası artan deformasyon oranı ile soğuk deformasyona tabi tutulmamış kompozit ve matris alaşımına göre maksimum sertlik değerlerinde belirgin bir artış elde edilmiştir.
Abstract: Both the development of the aesthetic dentistry and a favorable approach towards amalgam resulted in an increasing interest in using the composites in restoration of posterior teeth. The most important factor that limits composites the usage of posterior area is that they do not have enough resistance to wear and mastication strength. Physical properties such as wear; surface hardness and compressive strength are important factors choosing posterior composites. In this study, wear resistance, microhardness profile and compressive strength of three different composite materials offered for using in posterior area were investigated. The results have shown that the most resistance filling material was the Alert. The highest surface hardness values were found for the Valux–Plus. After applying compressive tests to the composite resins, The Valux–Plus material exhibited the highest compressive strength.
Abstract: PROBLEM TO BE SOLVED: To provide a catalytic electrode layer for a fuel cell, which can prevent highly dispersed catalytic particulates on a carbon nanofiber from flowing out.
SOLUTION: The catalytic electrode layer for the fuel cell has an nonwoven fabric nanofiber with the catalytic particulate supported thereon, wherein the carbon nanofiber has a nitrogen element with an aspect ratio (length/diameter ratio) in a range of 40 to 50,000, and the catalytic particulate combined with the nitrogen element.
