In this work, bio-inspired concepts, including a Self-Healing (SH) and super hydrophobic structure, were used to produce slow-release of urea fertilizer. Following a bottom-up process, an SH layer on the urea granule was produced from a combination of two natural waxes, palm and carnauba, and fabricated by a hot-melt coating process in a pan coater. Another layer for super hydrophobicity was formed by a deposition of submicron-wax and carbon black particles on the SH layer to create a micro-nanostructure during coating. After the heat treatment, a smooth coating and even deposition of waxes throughout the urea surfaces were obtained. The properties of the waxes, a healing mechanism, and releasing profiles were examined using an optical microscope. After cracking of the coated urea surface, the intrinsic self-healing behavior was stimulated by heating the samples above 45 °C, corresponding to high ambient daytime temperatures. Air-trapping behavior was observed at the interphase of the water and coated urea, creating super hydrophobic granule surfaces which act as an invisible layer for water-penetration protection. The releasing profiles of the coated urea in soil revealed that the releasing periods could be significantly extended to four-times longer than those of the uncoated urea.

中文翻译：

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生物启发的缓释尿素肥料表面结构

在这项工作中，采用了具有生物启发性的概念，包括自我修复（SH）和超疏水结构，来生产尿素肥料的缓释剂。在自下而上的过程之后，尿素颗粒上的SH层由两种天然蜡（棕榈蜡和巴西棕榈蜡）的组合制成，并通过锅包衣机中的热熔涂层工艺制成。通过在SH层上沉积亚微米蜡和炭黑颗粒，形成另一个超疏水性层，从而在涂覆过程中形成微纳米结构。热处理后，在整个尿素表面上获得了光滑的涂层，蜡的沉积均匀。使用光学显微镜检查蜡的性质，修复机理和释放曲线。涂层尿素表面开裂后，通过将样品加热到45°C以上（与白天较高的环境温度相对应），可以激发固有的自我修复行为。在水和涂覆的尿素的界面处观察到了空气捕获行为，形成了超疏水的颗粒表面，该表面充当了不渗透水的保护层。包膜尿素在土壤中的释放曲线表明，释放时间可以比未包膜尿素的释放时间延长四倍。