Yazar "Cetinkara, H. Ali" seçeneğine göre listele

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    EVALUATION OF THE EFFECTS OF SURFACE TREATMENTS ON DIFFERENT DENTAL CERAMIC STRUCTURES
    (Inst Za Kovinske Materiale I In Tehnologie, 2013) Erturk, Ergul; Dalkiz, Mehmet; Ozyilmaz, Emre; Akbas, H. Zehra; Cetinkara, H. Ali; Aykul, Halil
    The surface treatments applied to porcelain materials can be different overglaze methods, chemical interactions and polishing techniques. The aims of these methods are the most durable restoration and the smoothest surface. The smoothness attained with these processes is important due to the following reasons: reduction of the bacteria remaining in the pores of a surface, improvement of gingival health and esthetic view, and prevention of an abrasion of the opposite canal. The aim of this study is to assess different surface-finishing operations that are applied to widely used porcelains in prosthetic dentistry using SEM (a scanning electron microscope). In the experiments seven different surface finishing operations (sandpaper, rubber, Sof-Lex, HP paste, autoglaze, overglaze and ion exchange) were applied to four different commercial porcelains (IPS d. SIGN, Antagon, Ceramco 3, Vitadur Alpha). The effects of various surface-finishing operations on porcelain are micromorphologically evaluated (a SEM analysis). The results showed that the smoothest surfaces were obtained with the overglaze and autoglaze, followed by HP paste, rubber, Sof-Lex and sandpaper. In addition, the smoothness values of HP paste proved that it can be safely used in clinical surface-finishing operations.
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    Hardness Behavior of Alumina-Zirconia Nanocomposites Synthesized by Gel Process
    (Polish Acad Sciences Inst Physics, 2013) Sahin, O.; Hasde, A.; Gocmez, H.; Tuncer, M.; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.
    The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size. DOI: 10.12693/APhysPolA.123.299
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    Mechanical Properties of Nanocrystalline Tetragonal Zirconia Stabilized with CaO, MgO and Y2O3
    (Polish Acad Sciences Inst Physics, 2013) Sahin, O.; Demirkol, I.; Gocmez, H.; Tuncer, M.; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.
    The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000 degrees C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and Y2O3 addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with Y2O3 by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Fetch relation. DOI: 10.12693/APhysPolA.123.296
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    Production and Mechanical Behaviour of Biomedical CoCrMo Alloy
    (Iop Publishing Ltd, 2011) Sahin, O.; Tuncdemir, A. Riza; Cetinkara, H. Ali; Guder, H. Salih; Sahin, E.
    Cobalt-based alloy (Co-30Cr-5.5Mo) is produced by the investment casting process. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. SEM, XRD and microhardness tests are used to examine the mechanical properties of the material. The examined material exhibits the behaviour of indentation size effect (ISE). Our results reveal that Vickers and Knoop microhardness are dependent on indentation test load. The traditional Meyer's law, the proportional specimen resistance (PSR) model and the Hays-Kendall model (HK) are used to analyze the load dependence of the hardness. As a result, the Hays-Kendall model is found to be the most effective to determine the load-independent hardness H-LI of CoCrMo alloy.
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    Vickers and Knoop Indentation Microhardness Study of ?-SiAION Ceramic
    (Polish Acad Sciences Inst Physics, 2011) Guder, H. S.; Sahin, E.; Sahin, O.; Gocmez, H.; Duran, C.; Cetinkara, H. Ali
    In this paper, analysis and interpretation of mechanical property measurements of beta-SiAION ceramic were reported. Indentation microhardness of beta-SiAION ceramic was measured using the Knoop and Vickers indenters. The analysis of the Vickers indentation microhardness data reveals the reverse indentation size effect that is the apparent microhardness increases with increasing applied indentation test load. However, the Knoop indentation microhardness data exhibit indentation size effect that is the apparent microhardness increases with decreasing applied test load. The experimental Knoop microhardness data was analyzed using Meyer's law, elastic-plastic deformation model, proportional specimen resistance model, and Hays-Kendall's model. As a result, modified proportional specimen resistance model is found to be the most effective one for the load-independent (Hu) microhardness determination of the SiAION ceramic. It was seen that different models used to analyze the data obtained from the Vickers indentation do not give the same intrinsic hardness value. We also present the calculation of the Young modulus, E, of the beta-SiAION ceramic.