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198 results on '"Gokcekaya, Ozkan"'

6. Superimpositional design of crystallographic textures and macroscopic shapes via metal additive manufacturing—Game-change in component design

Author

Ishimoto, Takuya, Morita, Naotaka, Ozasa, Ryosuke, Matsugaki, Aira, Gokcekaya, Ozkan, Higashino, Shota, Tane, Masakazu, Mayama, Tsuyoshi, Cho, Ken, Yasuda, Hiroyuki Y., Okugawa, Masayuki, Koizumi, Yuichiro, Yoshiya, Masato, Egusa, Daisuke, Sasaki, Taisuke, Abe, Eiji, Kimizuka, Hajime, Ikeo, Naoko, and Nakano, Takayoshi

Published
2025
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40. Novel single crystalline-like non-equiatomic TiZrHfNbTaMo bio-high entropy alloy (BioHEA) developed by laser powder bed fusion

Author

0000-0002-9258-858X, Gokcekaya, Ozkan, 1000050508835, 0000-0003-0081-0591, Ishimoto, Takuya, Nishikawa, Yuki, Kim, Yong Seong, 1000010592529, 0000-0002-8427-7124, Matsugaki, Aira, 1000080845347, 0000-0002-2773-072X, Ozasa, Ryosuke, Weinmann, Markus, Schnitter, Christoph, Stenzel, Melanie, Kim, Hyoung Seop, Miyabayashi, Yoshitsugu, 1000030243182, 0000-0001-8052-1698, Nakano, Takayoshi, 0000-0002-9258-858X, Gokcekaya, Ozkan, 1000050508835, 0000-0003-0081-0591, Ishimoto, Takuya, Nishikawa, Yuki, Kim, Yong Seong, 1000010592529, 0000-0002-8427-7124, Matsugaki, Aira, 1000080845347, 0000-0002-2773-072X, Ozasa, Ryosuke, Weinmann, Markus, Schnitter, Christoph, Stenzel, Melanie, Kim, Hyoung Seop, Miyabayashi, Yoshitsugu, 1000030243182, 0000-0001-8052-1698, and Nakano, Takayoshi

Abstract

Gokcekaya O., Ishimoto T., Nishikawa Y., et al. Novel single crystalline-like non-equiatomic TiZrHfNbTaMo bio-high entropy alloy (BioHEA) developed by laser powder bed fusion. Materials Research Letters 11, 274 (2023); https://doi.org/10.1080/21663831.2022.2147406., This study developed a non-equiatomic Ti28.33Zr28.33Hf28.33Nb6.74Ta6.74Mo1.55 super-solid solutionized BioHEA using laser powder bed fusion (LPBF) to reach the full potential as BioHEA. We succeeded in significant suppression of elemental segregation, thus, resulting in a single crystalline-like texture by activating layer-to-layer epitaxial growth. Relatively low Young’s modulus was achieved in the single crystalline-like BioHEA. Moreover, LPBF-fabricated BioHEA exhibited significantly higher yield stress (1355–1426 MPa) due to the effective solid solution hardening compared to as-cast counterpart with marked segregation (949 MPa), and good biocompatibility. This is first report achieving BioHEA with low modulus, excellent strength-ductility balance, and good biocompatibility via LPBF.

Published
2023

44. Novel single crystalline-like non-equiatomic TiZrHfNbTaMo bio-high entropy alloy (BioHEA) developed by laser powder bed fusion

Author

Gokcekaya, Ozkan, primary, Ishimoto, Takuya, additional, Nishikawa, Yuki, additional, Kim, Yong Seong, additional, Matsugaki, Aira, additional, Ozasa, Ryosuke, additional, Weinmann, Markus, additional, Schnitter, Christoph, additional, Stenzel, Melanie, additional, Kim, Hyoung Seop, additional, Miyabayashi, Yoshitsugu, additional, and Nakano, Takayoshi, additional

Published
2022
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50. Influence of precursor deficiency sites for borate incorporation on the structural and biological properties of boronated hydroxyapatite

Author

Gokcekaya, Ozkan, Ergun, Celaletdin, Webster, Thomas J., 1000030243182, Nakano, Takayoshi, Gokcekaya, Ozkan, Ergun, Celaletdin, Webster, Thomas J., 1000030243182, and Nakano, Takayoshi

Abstract

Gokcekaya O., Ergun C., Webster T.J., et al. Influence of precursor deficiency sites for borate incorporation on the structural and biological properties of boronated hydroxyapatite. Ceramics International; https://doi.org/https://doi.org/10.1016/j.ceramint.2022.10.232., The biological properties of hydroxyapatite (HA) are significantly influenced by its compositional characteristics especially doping elements and/or Ca/P ratio, which can be altered by precursor chemistry. In this study, a group of boronated (B-incorporated) hydroxyapatite (BHA) was synthesized using a precipitation method by setting the Ca/P ratio to the stoichiometric value of HA (1.67), while altering the precursor chemistry by adjusting either (Ca + B)/P (Ca-deficient precursor, BC) or Ca/(P + B) (P-deficient precursor, BP). After heat-treatment, the partial decomposition of the BC was observed, forming tricalcium phosphate as the byproduct, however, the BP showed phase stability at all temperatures. The B-ionic species in the form of (BO₂)⁻ and (BO₃)³⁻ were incorporated into the HA structure at the (PO₄)³⁻ and (OH)⁻ positions, respectively. The incorporation of the B species also facilitated the incorporation of (CO₃)²⁻ groups specifically in the BPs. This is the first finding on BHA reporting that preferential (CO₃)²⁻ incorporation depends on the precursor chemistry used. As a result, osteoblast adhesion was superior on the BPs compared to pure HA owing to the carbonated structure, increasing cell spreading area. As such, this in vitro study highlighted that the present P-deficient precursor approach for synthesizing BHA improved biocompatibility properties and should, thus, be further considered for the next-generation of improved orthopedic applications.

Published
2022

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