李沛,李志,杨建成,袁静.镁合金表面DCPD涂层的制备及其界面结合机制研究[J].表面技术,2024,53(4):193-199, 210.
LI Pei,LI Zhi,YANG Jiancheng,YUAN Jing.Preparation of DCPD Coating on Magnesium Alloy and Its Interface Bonding Mechanism[J].Surface Technology,2024,53(4):193-199, 210 |
| 镁合金表面DCPD涂层的制备及其界面结合机制研究 |
| Preparation of DCPD Coating on Magnesium Alloy and Its Interface Bonding Mechanism |
| 投稿时间：2023-01-12 修订日期：2023-05-05 |
| DOI：10.16490/j.cnki.issn.1001-3660.2024.04.018 |
| 中文关键词: 镁合金 DCPD涂层 界面结合能 界面结合位点 分子动力学模拟 |
| 英文关键词:magnesium alloy DCPD coating bonding energy interface bonding molecular dynamics simulation |
| 基金项目:青海省卫生健康委员会指导性计划课题(2021-wjzdx-33);中国科学院西部之光人才培养计划“西部青年学者项目” |
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| Author | Institution |
| LI Pei | Second Ward of Orthopedics, Qinghai Provincial People's Hospital, Xining 810017, China |
| LI Zhi | Second Ward of Orthopedics, Qinghai Provincial People's Hospital, Xining 810017, China |
| YANG Jiancheng | Second Ward of Orthopedics, Qinghai Provincial People's Hospital, Xining 810017, China |
| YUAN Jing | School of Physics and Electronic Information Engineering, Qinghai Minzu University, Xining 810007, China |
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| 中文摘要: |
| 目的 研究CaHPO4×2H2O(DCPD)与Mg的界面结合机制，以提高DCPD在镁合金表面的界面结合强度。方法 利用电镀法在AZ31镁合金表面制备DCPD涂层，采用SEM、XRD、XPS等对涂层形貌及结构进行表征。同时，运用分子动力学模拟(MD)对DCPD在Mg表面形成机制进行研究，通过统计界面层中不同组分的径向分布函数、密度分布、均力势、总能量等的变化，揭示DCPD/Mg的界面结合能、结合位点及结合方式。结果 通过电镀法形成的DCPD涂层形貌为致密的荷花瓣状晶体，主要成分为CaHPO4×2H2O。模拟结果表明，CaHPO4.2H2O的4个晶面(010)、(−120)、(11−1)、(111)、(−120)与Mg的结合能最强(163.63 kJ/mol)。其中起“铆钉”作用的基团是HPO42−和H2O，结合位点主要为O与Mg，即HPO42−和H2O通过静电作用及范德华力与Mg形成Mg-HPO42−和Mg-H2O偶极对。研究发现，形成的偶极对中HPO42−及H2O的配位数分别为0.75和1.16，Mg-H2O的解离能更大，结构更稳定。结论 提出改善DCPD/Mg结合强度的方法，电镀前可将镁合金置于NH4H2PO4溶液中浸泡片刻，促进CaHPO4×2H2O(−120)晶面的形成。 |
| 英文摘要: |
| To improve the bonding force of the CaHPO4×2H2O (DCPD) coating on magnesium alloys, the work aims to propose an approach for synthesizing calcium phosphate coating on the surface of magnesium alloy via electroplating. The morphology, microstructure, and interface bonding of the calcium phosphate coating were characterized by a combination of different characterization techniques (SEM, XRD and XPS) and molecular dynamics simulation (MD). The formation of lotus-shape-like calcium phosphate coating, namely its main component, was CaHPO4×2H2O. MD simulation was used to analyze the interfacial morphology, radial distribution function (RDF), the potential of mean force (PMF), total energy, interface bonding energy, and relative concentration. The interface bonding energy, mutual bonding site, change in interface structure, and micro bonding mechanism between Mg and DCPD coating were further investigated. The main conclusions included three aspects:(1) Among the four common crystal planes of the DCPD coating, namely layer (010), layer (–120), layer (11–1), and layer (111), the layer (–120) had the strongest interface bonding force with Mg (001), which was 39.09 kcal/mol; (2) The main components of CaHPO4×2H2O could be simply divided into Ca2+, HPO42– and H2O. Among them, the relative contents of HPO42– and H2O in the interface layer were higher, indicating that the groups acting as rivet groups in the two-phase interface layer were HPO42– and H2O groups. The bonding sites were mainly effective interactions between O and Mg atoms. In other words, HPO42– and H2O groups could form Mg-HPO42– and Mg-H2O dipole pairs with Mg through electrostatic interaction and Van der Waals force; (3) The coordination number of Mg-HPO42– and Mg-H2O dipole pairs were 0.75 and 1.16, respectively, and their molar ratio was close to 1:1. Thus, one Mg atom on the DCPD/Mg interface was closely bound with one HPO42– or one H2O. The coordination number of Mg-H2O dipole pair might be larger due to its higher concentration in the DCPD coating; (4) Compared with Mg-HPO42– dipole pairs, there were more H2O molecules closely bound to Mg atom, forming Mg-H2O dipole pairs, and its dissociation energy (4.23 kJ/mol) was also higher than that of Mg-HPO42– (2.85 kJ/mol). The reason for its higher dissociation energy might be due to the volume of H2O smaller than that of HPO42−, which was easy to rotate in the lattice, thus forming a more stable bonding with Mg. Furthermore, based on the above research, two feasible schemes are proposed to improve the interface bonding energy of DCPD coating and magnesium alloy. The magnesium alloy surface is pretreated before electroplating. Specifically, the magnesium alloy is immersed in NH4H2PO4 solution for a period, so that the H2O and HPO42– groups can better bond with the Mg substrate, thus improving the bonding force of the Mg substrate and DCPD coating interface. |
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