1,721,043 research outputs found
Drilling of a hybrid Al/SiC/Gr metal matrix composites
No full textThe present study investigates the influence of cutting parameters on cutting force and surface roughness in drilling of Al/20%SiC/5%Gr and Al/20%SiC/10%Gr hybrid composites fabricated by vortex method. The drilling tests are conducted with diamond-like carbon-coated cutting tools. This paper is an attempt to understand the machining characteristics of the new hybrid metal matrix composites. The results indicate that inclusion of graphite as an additional reinforcement in Al/SiCp reinforced composite reduces the cutting force. The cutting speed and its interactions with feed rate are minimum. Feed rate is the main factor influencing the cutting force in both composites. The surface roughness value is proportional with the increase in feed rate while inversely proportional with cutting speed in both composites. For all cutting conditions, Al/20%SiC/10%Gr composite has lower surface roughness values than Al/20%SiC/5%Gr composite. The surface is analyzed using scanning electron microscope
Taxonomical and chorological notes on the Turkish endemic Bupleurum pendikum Snogerup (Umbelliferae)
Full text linkAslan, Serdar/0000-0002-7021-7702WOS: 000288779300087Bupleurum pendikum Snogerup is a local endemic species known from only two localities in western Turkey. After the rediscovery of Bupleurum pendikum, it has been recorded from a new locality in Kocaeli province. Brief history, morphology, habitat and ecology of this endemic species have been discussed in this research. The conservation status of Bupleurum pendikum is also reviewed based on the present distribution data.Evren Koprulu (AKIFER), TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [DFG 2225]; BGBM HerbariumThe authors would like to thank Evren Koprulu (AKIFER), TUBITAK-DFG 2225 scholarship program and BGBM Herbarium for their financial support, Neriman Ozhatay, Tuna Ekim, Tamer Ozcan, Dilek Demir Oral, Burcu Ceylan, Asli Dogru Koca, Adele Smith and Mustafa Keskin for their help and valuable comments
A new record for Turkey: Michauxia nuda A.DC. (Campanulaceae)
Full text linkAslan, Serdar/0000-0002-7021-7702WOS: 000276167100007Michauxia nuda A.DC. (Campanulaceae) is recorded for the first time (C8 Siirt province) from Turkey. The diagnostic characters of M. nuda are described and its habitat and conservation status are indicated. Besides, it is illustrated, and a distribution map is presented. Notes on collecting number of type specimen of this species are provided.Nature Society (Doga Dernegi)We would like to thank Nature Society (Doga Dernegi) for their financial support, herbaria of K and G. for making it possible for us to compare our specimens with the images of specimen, and Mesut Hiirkul (AEF) for allowing us to see the specimen of Michauxia thyrsoidea, and A. Emre Yaprak, G. Nilhan Tug, Necmi Aksoy for their help and valuable comments
Characteristics of electro-co-deposited Ni-Al2O3 nano-particle reinforced metal matrix composite (MMC) coatings
No full textIn the present work, Ni/Al2O3 metal matrix composite (MMC) coatings were prepared from a modified Watt's type electrolyte containing nano-alpha-Al2O3 particles by direct current (DC) plating method to increase the surface hardness and wear resistance of the electrode posited Ni. For these purposes, particle concentration in electrolyte, the effect of surfactant concentration, current density, and bath pH, etc. were investigated for optimization to obtain high quality coatings. Al2O3 nano-powders with average particle size of 80 nm were co-deposited with nickel matrix on the steel substrates. The depositions were controlled to obtain specific thickness (between 50 and 200 mu m) and particle volume fraction in the matrix (between 0.03 and 0.12). The characterization of the coatings was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) facilities. The hardness of the resultant coatings was also measured and found to be 280-641 Hv depending on the particle volume in the Ni matrix. The effects of the surfactant on the zeta potential, co-deposition, and distribution of Al2O3 particles in nickel matrix, and tribological properties of composite coatings were investigated. The results showed that the wear resistance of the nano-composites was approximately 2-3.5 times increased compared with unreinforced Ni deposited material. (C) 2009 Elsevier B.V. All rights reserved
Thermal Expansion and Thermal Conductivity Behaviors of Al-Si/SiC/graphite Hybrid Metal Matrix Composites (MMCs)
No full textEffect of Reciprocating Sliding Speed on the Tribological Performance of Nano SiCp Reinforced Ni-Metal Matrix Composites Produced by Electrocodeposition
No full textIn the present work, Ni/SiC metal matrix composite (MMC) coatings were prepared from a modified Watt's type electrolyte containing nano-SiC particles by direct current (DC) plating method to increase wear resistance of the electro co-deposited Ni. SiC nano particles with average particle size of 0, 1-1,(,mu m were co-deposited with nickel matrix on the steel substrates. For this purpose, several studies were carried out to optimize deposition parameters for specific applications. The depositions were controlled to obtain the specific thickness (between 175-200 mu m) and particle volume fraction in the matrix (between 0.03 and 0.10). The hardness of the resultant coatings was measured and found to be 280-571 HV depending on the particle concentration in the electrolyte and therefore, particle volume in the Ni matrix. The tribological tests were performed by a reciprocating ball-on disk apparatus sliding against M50 steel ball ((sic)10 mm). All the friction and wear tests were performed under the unlubricated conditions at room temperature and in the ambient air (relative humidity 55-65%). The wear tests were carried out at different sliding velocities of 50 mm/s, 100 mm/s and 150 mm/s by using a constant dead load of 1.0 N. It was detected that increasing sliding speed resulted to increase wear rate but decreasing friction coefficient due to change in wear mechanism. Increasing sliding speed showed formation of tribo induced oxides up to 20 g/l SiCp in the electrolyte and wear mechanism was controlled by temperature induced fatigue wear. Further increase in the SiCp in the electrolyte caused an abrasive type of the wear
Nano Crystalline TiO2 Thin Films as Negative Electrodes for Lithium Ion Batteries
No full textIn this study, rutile (tetragonal, P42/mnm), anatase (tetragonal, I41/amd) polymorphs of titanium dioxide films were synthesized successfully magnetron sputtering of titanium films on stainless steel substrates followed by in situ direct current plasma oxidation. The as-prepared titanium dioxide thin films were oxidized at 75 W, 100 W and 125 W plasma powers in order to optimize the system with best electrochemical performance. The mean grain sizes of the deposited films were found to be in the range of 14.2-12.9 nm as revealed by the scanning electron microscopy and X-ray diffractometer studies. The electrochemical studies were performed with pure metallic lithium foil cathode with the best performing nano structured titanium dioxide as anode. The specific capacity of the nanocrystalline titanium dioxide films oxidized at 125 W direct current was 207 mA h g(-1) even after 20 cycles in the 0.02-2 V region, indicating excellent cycling stability and reversibility
EFFECT OF ALTERNATIVE HEAT-TREATMENT PARAMETERS ON THE AGING BEHAVIOR OF SHORT-FIBER-REINFORCED 2124 Al COMPOSITES
No full textThe 2124 Al alloy and a composite of the 2124 Al alloy reinforced with 20 % of volume fractions of delta-Al2O3 short fibers made by squeeze casting were subjected to controlled and systematic aging treatments. The materials were solution treated at (495, 525 and 555) degrees C. After quenching, the matrix alloy and the composite were artificially aged at (160, 170, 180 and 190) degrees C up to 36 h. The aging was monitored with hardness measurements and differential scanning calorimetry. The time required to reach the peak hardness of the composite matrix during a precipitation treatment was shorter than that for the unreinforced 2124 Al. An increase in the solution-treatment temperature resulted in an increase of the composite-matrix hardness. The delta-Al2O3-reinforced composite exhibits no grain-boundary melting, but appears to show incipient melting around short alumina fiber interfaces at temperatures above 525 degrees C. The highest HV value was obtained after solutionizing at 495 degrees C for 6 h, followed by water quenching and aging at 190 degrees C for 10 h for the unreinforced matrix alloy. In the case of the reinforced alloy the highest HV value was found after solutionizing at 555 degrees C for 6 h, quenching and aging at 170 degrees C for 12 h
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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