title: c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus).
abstract: Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance.
authors.affiliation: Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
authors.forename: Jimin
authors.initials: J
authors.lastname: Fu
authors.affiliation: Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
authors.forename: Chong
authors.initials: C
authors.lastname: He
authors.affiliation: AML, Department of Engineering Mechanics and Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Xia
authors.affiliation: AML, Department of Engineering Mechanics and Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Applied Mechanics, Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Feng
authors.affiliation: Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
authors.forename: Qifang
authors.initials: Q
authors.lastname: Yin
authors.affiliation: The State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xinghua
authors.initials: X
authors.lastname: Shi
authors.affiliation: AML, Department of Engineering Mechanics and Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Feng
authors.affiliation: Institute of Applied Mechanics, Zhejiang University, Hangzhou, Zhejiang 310027, China.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
authors.forename: Haimin
authors.initials: H
authors.lastname: Yao
mesh_terms: D000818:Animals; D002347:Carps / Q000502:physiology*; D017886:Durapatite / Q000737:chemistry*; D014070:Tooth / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D017886:Durapatite