A methodology of surface chemical functionalization of equimolar HfNbTaTiZr high-entropy alloy (HEA) is presented herein. The aim is to improve the biocompatibility of this material for its application as bio-implants. X-ray Photoelectron Spectroscopy (XPS) showed that air or aqueous oxidation of HfNbTaTiZr induced the formation at its surface of unmixed monometallic oxides: TiO₂, Nb₂O₃, ZrO₂, Hf₂O₃, and Ta₂O₅. Besides, it was observed that short (2 h) mild aqueous oxidation (without H₂O₂) retains the surface stoichiometry of these elements compared to a more aggressive one (with H₂O₂). The mild oxidation was retained to form a sol-gel chemistry platform for HfNbTaTiZr surface silanization. In practice, the oxidized HfNbTaTiZr surface was reacted with 2-methoxy [(polyethyleneoxy)_6–9 propyl] trimethoxysilane (MPTMS), dissolved in distilled ethanol, under an inert atmosphere. Both, the precursor concentration and the reaction time, were varied to define the optimized operating conditions. Infrared spectroscopy performed on all prepared samples, within an attenuated total reflectance (ATR) sampling configuration, evidenced the well-known vibrational signatures of SiO and CH bonds at 1090 cm⁻¹ and 2980 cm⁻¹, respectively, confirming silane grafting, and showed that the intensity of these bands increases when the reaction time and/or the siloxane precursor concentration increase. Moreover, XPS showed that a reaction time of 48 h is required to completely cover the alloy surface with an organic layer (exhibiting a thickness larger than the XPS analysis depth). Finally, as a preliminary study, mildly oxidized alloy and the grafted one for a reaction time of 48 h were contacted to a Phosphate-Buffered Saline (PBS) solution and a standard Nutrient Mixture for cell cultures, the well-known Dulbecco's Modified Eagle Medium (DMEM), up to one month to check their chemical stability. None metal release was evidenced for the treated sample highlighting the importance of surface processing before any bio-implant use.

本文介绍了等摩尔HfNbTaTiZr高熵合金（HEA）的表面化学功能化方法。目的是为了提高这种材料作为生物植入物的生物相容性。X射线光电子能谱（XPS）表明，HfNbTaTiZr的空气或水氧化引起未混合的单金属氧化物：TiO ₂，Nb ₂ O ₃，ZrO ₂，Hf ₂ O ₃和Ta ₂ O ₅在其表面形成。此外，观察到短时间（2小时）温和的水氧化（无H ₂ O ₂）相比更具腐蚀性的元素（使用H ₂ O ₂）保留了这些元素的表面化学计量。保留轻度的氧化以形成用于HfNbTaTiZr表面硅烷化的溶胶-凝胶化学平台。实际上，在惰性气氛下，将氧化的HfNbTaTiZr表面与溶解在蒸馏乙醇中的2-甲氧基[（聚乙烯氧基）_6-9丙基]三甲氧基硅烷（MPTMS）反应。改变前体浓度和反应时间以定义最佳的操作条件。在衰减的全反射率（ATR）采样配置下，对所有准备好的样品进行的红外光谱分析证明了在1090 cm ^-1处众所周知的Si O和C H键的振动特征和2980厘米^-1分别证实了硅烷接枝，并表明当反应时间和/或硅氧烷前体浓度增加时，这些带的强度增加。此外，XPS显示，要用有机层完全覆盖合金表面（厚度大于XPS分析深度），需要48小时的反应时间。最后，作为一项初步研究，将轻度氧化的合金和嫁接的合金在48小时的反应时间内与磷酸盐缓冲盐水（PBS）溶液和用于细胞培养的标准营养混合物（众所周知的Dulbecco改良的Eagle培养基）接触（DMEM），长达一个月以检查其化学稳定性。没有证据表明处理过的样品有金属释放，突出了在使用任何生物植入物之前进行表面处理的重要性。